Biomedical subjects

Mehmet Kaya

Publications and source records attributed to Mehmet Kaya.

28 records · Page 2Linked to original sources

PubMed2002

Effects of losartan on the blood-brain barrier permeability in long-term nitric oxide blockade-induced hypertensive rats.

Hypertension is closely associated with vascular endothelial dysfunction. The aim of this study was to investigate the effects of Angiotensin II (ANG II) receptor antagonist losartan on the blood-brain barrier (BBB) permeability in L-NAME-induced hypertension and/or in ANG II-induced acute hypertension in normotensive and hypertensive rats. Systolic blood pressure was measured by tail cuff method before, during and following L-NAME treatment (1 g/L). Losartan (3 mg/kg) was given to the animal for five days. Acute hypertension was induced by ANG II (60 microg/kg). Arterial blood pressure was directly measured on the day of the experiment. BBB disruption was quantified according to the extravasation of the albumin-bound Evans blue dye. Losartan significantly reduced the mean arterial blood pressure from 169 +/- 3.9 mmHg to 82 +/- 2.9 mmHg in L-NAME and from 171 +/- 2.9 mmHg to 84 +/- 2.9 in L-NAME plus losartan plus ANG II groups (p < 0.05). The content of Evans blue dye in the cerebral cortex significantly increased in L-NAME (p < 0.01). Moreover, the content of Evans blue dye markedly increased in the cerebellum (p < 0.001) and slightly increased in diencephalon region (p < 0.05) in L-NAME plus ANG II. Losartan reduced the increased BBB permeability to Evans blue dye in L-NAME (p < 0.01) and L-NAME plus ANG II (p < 0.001). These results indicate that L-NAME and L-NAME plus ANG II both lead to an increase in microvascular Evans blue dye efflux to brain, and losartan treatment attenuates this protein-bound dye transport into brain tissue presumably due to its protective effect on endothelial cells of brain vessels.

Angiotensin II↗

PubMed2002

Compound muscle action potential analysis in different death models: significance for the estimation of early postmortem interval.

In this experimental study, we investigated the varieties of excitability of gastrocnemius muscle via sciatic nerve as per different death models (asphyxia, abundant-bleeding and gradual-bleeding) on rats and the significance for the estimation of postmortem interval was evaluated. For this purpose, the rats were applied different stimulus intensities (5, 20, 40 mA) with 0.1 ms duration, before, during and every 5 min after death, using rectangular impulses, and the mean amplitude, onset latency and area values for each compound muscle action potential (CMAP) were elicited. It was detected that amplitude and area increased and onset latencies prolonged in the first postmortem 15 min. From the 15 min, CMAP area and amplitude showed an ever-increasing decrease and the prolongation of onset latencies became apparent. The decrease rate of area and amplitude was found to be statistically significantly different in asphyxia and abundant-bleeding models compared with in gradual-bleeding model, at 30 min measurements. However, there was not any significant difference in onset latency increase rates of three groups. Separately, any significant correlation between the agony and excitability periods among the groups could not be detected. The fact that the increase rate of onset latency did not show a significant difference as per death models indicated that onset latency ratios would be more appropriate criteria in determination of postmortem interval, regardless the reason of death.

Action Potentials↗

PubMed2002

Effects of acute cold exposure on blood-brain barrier permeability in acute and chronic hyperglycemic rats.

These experiments were carried out to study, the effects of cold exposure on the permeability of blood-brain barrier (BBB) in hyperglycemic rats. The integrity of the BBB was investigated using Evans blue albumin (EBA) extravasation. Serum glucose levels in hyperglycemic rats were significantly higher than that obtained from normoglycemic rats (P < 0.05). Mean arterial blood pressure in hypothermic groups significantly dropped into lower levels, than that obtained in normothermic groups (P < 0.05). The EBA extravasation to the cerebellum in the group of cold exposure+acute hyperglycemia significantly increased compared with the values obtained from the cold exposure group (P < 0.05). The EBA extravasation to the brain regions of diabetic rats exposed to cold increased more than that in normotermic control rats (P < 0.05), but did not exceed the levels in cold controls. The result of this study suggests that, acute hyperglycemia superimposed upon the permeability of BBB in the rat exposed to cold, only in selected regions of the brain, especially the cerebellum, and this result could be an important factor to explain the mechanisms of death related with hyperglycemia+cold exposure in forensic medicine.

Acute Disease↗

PubMed2002

Catalase and alpha-tocopherol attenuate blood-brain barrier breakdown in pentylenetetrazole-induced epileptic seizures in acute hyperglycaemic rats.

Experimental data indicate that acute hyperglycaemia can aggravate the consequences of epileptic seizures on the permeability of the blood-brain barrier (BBB). The purpose of this study was to examine the effects of chronic administration of alpha -tocopherol (vitamin E) and acute catalase administration on the disrupted BBB during experimentally pentylenetetrazole-induced status epilepticus in acute hyperglycaemic rats. The integrity of the BBB was tested using the Evans Blue (EB) dye extravasation. The concentration of EB dye was measured in four regions of the brain. Epileptic seizures induced a significant increase in EB dye extravasation in the brain regions compared with that of the groups of rats treated with saline, glucose, catalase and alpha -tocopherol (P< 0.01). The content of EB dye in the brain regions of animals in the acute hyperglycaemia plus epileptic group was higher than that of the saline, glucose, catalase, alpha -tocopherol and epileptic groups (P< 0.01). The increased EB dye transfer from blood to the brain in status epilepticus and acute hyperglycaemia plus status epilepticus was attenuated by the treatment with catalase and alpha -tocopherol. These data suggest that a partial reduction in the production of reactive oxygen species by catalase and alpha -tocopherol contributes to decreases in the content of EB dye across the BBB during pentylenetetrazole-induced status epilepticus in acute hyperglycaemic rats.

Acute Disease↗

PubMed2002

Rothmund-Thomson syndrome: a case report.

Rothmund-Thomson syndrome (RTS) is an extremely rare genetic disorder characterized by poikilodermatous skin changes, photosensitivity, and an increased risk of developing skin and bone malignancies. In this case report, the dental and periodontal features of RTS in a 16-year-old female patient are presented. The transmission electron microscopy performed on a gingival biopsy specimen showed structural defects of connective tissue. If the unusual ultrastructural findings of this case are confirmed as being consistent with other RTS patients, it is our opinion that this syndrome can be considered among the systemic diseases associated with early-onset periodontitis.

Adolescent↗

PubMed2002

Effects of excitotoxic median raphe lesions on scopolamine-induced working memory deficits in inhibitory avoidance.

The aim of the present study was to investigate the effects of excitotoxic damage of the serotonergic cell bodies in the median raphe nucleus (MRN) on the scopolamine-induced working memory deficits in a single-trial light/dark inhibitory avoidance task. Rats were given 1 mg/kg of scopolamine hydrobromide (intraperitonal, i.p.) or saline before the inhibitory avoidance training, in which initial preference to the dark compartment (escape latency) was used to measure nonmnemonic behaviors, and response latency to enter the dark compartment immediately after the shock was used to measure working memory. It was found that scopolamine significantly reduced escape latencies in sham-lesioned rats, whereas it had no effect in the rats with MRN lesions. Although MRN lesion per se did not alter response latency, it prevented scopolamine-induced decrease in this parameter. These results suggest that the antagonistic interactive processes between serotonergic projections of the MRN and the muscarinic cholinergic system modulate nonmnemonic attentional component of working memory formation in the inhibitory avoidance.

Alzheimer Disease↗

PubMed2002

Frequency of cardiac troponin-t elevation after successful direct stenting.

Direct stenting (stenting without balloon predilation) is a novel approach in percutaneous treatment of coronary artery lesions. This approach may also significantly lower the rate of procedural ischaemic complications by reducing aggression to the vessel wall and immediately sealing the dissections created due to balloon inflation by the endoprosthesis. However, the incidence of minor myocardial infarction after direct stenting is unknown. The purpose of this study was to measure cTnT, creatine kinase and its isoform, CK-MB after apparently successful elective stent implantation without balloon predilation. Enzyme levels were measured just before and 16 hours after the procedures. A second-generation commercial ELISA cTnT assay (Boehringer Mannheim Corporation) was used to measure cTnT with a cutoff of 0.1 ng/dl. There was no abnormality in all three enzymes before the procedure. CTnT was elevated in 6 patients (13.6%), CK and CK-MB were elevated in 1 (2.3%) patient at 16 hours after the procedure. Both CK and CK-MB elevation were observed in the patient with side branch occlusion. In all others cTnT measurements in addition to CK-MB measurements are needed to detect this minor myocardial damage. To the best of our knowledge this is the first report evaluating the incidence of myocardial injury after direct stenting. Direct stenting by avoiding balloon-induced complications may decrease procedural myocardial necrosis. Randomized studies with larger patient populations should be conducted to compare this approach with conventional stenting. CTnT measurements in addition to CKMB measurements are essential in detecting this minor myocardial damage.

Aged↗

PubMed2002

Sidebranch occlusion after coronary stenting with or without balloon predilation: direct versus conventional stenting.

Direct stenting (DS) is a novel approach in percutaneous treatment of coronary artery lesions. Several studies confirmed the safety and feasibility of the procedure with success rates greater than 90%. However, the data regarding the incidence of sidebranch occlusion (SBO) after DS are scarce. The purpose of this study was to evaluate SBO (> 1 mm) after DS and compare it to conventional stenting (CS) with balloon predilation. The study population consisted of 151 patients (88 underwent DS, 63 underwent CS) with 185 sidebranches jailed by the stent (110 in DS group, 75 in CS group). SBO was observed in 20 out of 110 patients in the DS group (18.2%) and 18 out of 75 patients in the CS group (24%). Although the incidence of SBO was higher in the CS group compared to the DS group (24% vs. 18.2%, respectively), these values did not reach statistical significance (p > 0.05). Most of the SBOs were observed in cases with type D sidebranch morphology (p < 0.001) and in cases with sidebranch ostial diameter stenosis 50% (p = 0.019). None of the other clinical and angiographic variables predicted the SBO. To the best of our knowledge, this is the first report comparing incidence of SBO between two different PCI methods (CS vs DS). Randomized studies with larger patient populations should be conducted to compare this approach with conventional stenting.

Aged↗

PubMedDate not supplied

Tylosin does not affect GnRH-induced LH secretion in rams.

The aim of this study was to investigate the effect of a therapeutic dose of Tylosin (Tylan 50) on gonadotropin releasing hormone (GnRH)-induced luteinizing hormone (LH) secretion in sheep. A total of 10 mature rams were divided into two groups by balancing body weights (bw) and body condition scores. Five of the rams received 10mg/kg Tylosin intramuscularly (i.m., Tylosin group), while the other five were given placebo (Control group), for 5 days. On Day 5, all the rams were injected intravenously (i.v.) with the GnRH agonist Ovarelin at 0.1 microg/kg bw. Blood samples were collected at -30, 0, 30, 60, 90, 120, 150, 180, 210, 240, and 270 min for measuring LH levels in the plasma. Three days after the cessation of Tylosin application (Day 8) the injection of GnRH was repeated at the same dose. Although LH secretion appeared to be lower on Day 8 compared to Day 5, there were no significant differences between the groups for the mean LH concentrations, total LH secretion, peak LH concentrations, timing of LH peak, duration of LH secretion, and LH secretions on Days 5 and 8. These results indicate the absence of a negative effect of a therapeutic dose of Tylosin on GnRH-induced LH secretion in rams.

Animals↗

PubMedDate not supplied

Regenerative effects of pulsed magnetic field on injured peripheral nerves.

Previous studies confirm that pulsed magnetic field (PMF) accelerates functional recovery after a nerve crush lesion. The contention that PMF enhances the regeneration is still controversial, however. The influence of a new PMF application protocol (trained PMF) on nerve regeneration was studied in a model of crush injury of the sciatic nerve of rats. To determine if exposure to PMF influences regeneration, we used electrophysiological recordings and ultrastructural examinations. After the measurements of conduction velocity, the sucrose-gap method was used to record compound action potentials (CAPs) from sciatic nerves. PMF treatment during the 38 days following the crush injury enhanced the regeneration. Although the axonal ultrastructures were generally normal, slight to moderate myelin sheath degeneration was noted at the lesion site. PMF application for 38 days accelerated nerve conduction velocity, increased CAP amplitude and decreased the time to peak of the CAP. Furthermore, corrective effects of PMF on. the abnormal characteristics of sensory nerve fibers were determined. Consequently, long-periodic trained-PMF may promote both morphological and electrophysiological properties of the injured nerves. In addition, corrective effects of PMF on sensory fibers may be considered an important finding for neuropathic pain therapy.

Action Potentials↗