Zeynep Sevim Ercan

Early phase alterations in endothelium dependent vasorelaxation responses due to aneurysm clip application and related manipulations

SummaryMechanically induced vasoconstriction observed throughout surgery and in the immediate postoperative period was investigated to assess the effects of various microsurgical manipulations.Factors such as the type of aneurysm clip, duration of temporary clipping and peri-adventitial tissue stripping were the variables in this study. Microsurgical clips were applied on guinea pig “cervical carotid arteries” in which peri-adventitia had been removed microsurgically. Arterial rings were removed immediately after surgery. Endothelium dependent relaxations were measured and morphological investigations were performed using light microscopy.It was observed that as the clip application period increased, relaxation responses decreased. Peri-adventitial tissue stripping caused a marked decrease in the relaxation responses in all types of the clips. Microvascular clips, in spite of their lower closing forces, had the greatest deleterious effect on relaxation responses of the vessel, in both normal and peri-adventitial tissue stripped. When the peri-adventitial tissue of the vessel had been stripped, convolutions of the lamina elastica interna were found to be lost in parallel with the decreased tonus of the artery. In the vessels subjected to clipping endothelial denudation and cracking took place.As a conclusion it can be stated that both peri-adventitial tissue stripping and microvascular clip application have deleterious effects in the early postoperative period. While choosing clips from minimal occlusion force tables, care must be taken to choose clips with less width; and while performing microvascular anastomosis, temporary clips with a lesser width must be used in place of microvascular clips. Adventitial stripping must not be unnecessarily generous during microvascular anastomosis.

A Cannabinoid Ligand, Anandamide, Exacerbates Endotoxin-Induced Uveitis in Rabbits

PURPOSE This study aimed to investigate the effects of anandamide or arachidonylethanolamide (AEA), an endogenous cannabinoid receptor agonist, on intraocular inflammation in an endotoxin-induced uveitis (EIU) model in rabbits. METHODS Forty New Zealand albino male rabbits were used (5 groups, 8 animals in each). After establishment of sufficient anesthesia, animals were taken under surgery for intravitreal injections. A maximum amount of 50 μL of solution was injected into the central vitreous with a 30-gauge needle. In the control group, sterile saline was injected into the right eyes of the animals. Likewise, AEA (10(-5) M) in the second group, lipopolysaccharide (LPS; 100 ng) in the third group, and AEA (10(-5) M) and LPS (100 ng) in the fourth group were administered. Fifth group received 0.1 mL subtenon injection of AM251 (10(-5) M), a CB(1)-receptor antagonist, 30 min prior to intravitreal LPS (100 ng) and AEA (10(-5) M) injection. At 24 h after the surgical intervention, clinical evaluation was performed and animals were then euthanized with 100 mg/kg intravenous pentobarbital injections. Immediately after the induction of pentobarbital anesthesia, the anterior chamber of the eyes was quickly punctured using a 30-gauge needle to drain aqueous humor (AH) and obtained specimens were used for cell count, protein measurement, and microbiological contamination tests. After AH collection, enucleation was performed and enucleated material was kept for the pathological evaluation. RESULTS AEA caused an overall worsening of EIU in studied eyes. It significantly increased the detrimental effects of endotoxin, as assessed by clinical investigation of ocular inflammation, AH leukocyte content, and AH protein concentrations. CB(1)-receptor antagonist AM251 administration reversed some components of this AEA-induced exacerbation to significant extents. CONCLUSION AEA exacerbated EIU in rabbit eyes. AM251 has been found beneficial to prevent AEAs aggravating impact on EIU. As AEA is a treatment choice for lowering intraocular pressure in ophthalmology practice, concurrent use of CB(1)-receptor antagonists may be a questionable strategy in cases of secondary glaucoma, to avoid aggravation of the present inflammation.

Effects of Varicocele on Electrical Field Stimulation-Induced Biphasic Twitch Responses in the Ipsilateral and Contralateral Rat Vasa Deferentia

Aim: Although little is known about the mechanisms, varicocele is considered as one of the factors leading to male infertility. Since reduced motility of the vas deferens was shown to contribute to male infertility, in this study we aimed to investigate the effect of varicocele on electrical field stimulation (EFS)-induced biphasic contractions of the vas deferens in order to evaluate the effect of varicocele on the motility of the vas deferens. Material and Methods: A total of 26 Sprague-Dawley rats (200–250 g) were assigned randomly into two groups: sham (n = 10) and varicocele (n = 16). Varicocele was produced by partial obstruction of the left renal vein. Four weeks after the surgical procedure, vasa deferentia were harvested and EFS-induced responses were recorded from the strips prepared from ipsilateral and contralateral sides via Grass isometric force displacement transducers. Exogenous α-β methyl ATP was applied at the concentration of 10–5M to the vasa deferentia strips, and exogenous noradrenalin was applied cumulatively at the concentrations between 10–7 and 10–4M. At the end of each experiment, 80 mM KCl was applied to induce contractions. All contractions were expressed as the percentage of the 80 mM KCl-induced contractions. Results: Varicocele significantly inhibited both phases of EFS-induced biphasic contractions in the ipsilateral side, whereas in the contralateral site it did not produce any change. However, there was no change in exogenously applied α-β methyl ATP, noradrenalin and KCl-evoked contractions of the vasa deferentia obtained from both sides. Conclusions: These results suggest that varicocele affects the ipsilateral vas deferens motility by reducing neurotransmitter release.

The effect of tryptophan administration on ileum contractility and oxidant status in mice

Summary.L-Tryptophan (TRP) is the precursor amino acid for the synthesis of serotonin (5-HT). 5-HT is effective both on the food intake and gastrointestinal system contractility. The aim of this study was to search the effects of systemic TRP treatment on 5-HT levels of ileum and searching the effect of ileal contractility and oxidant status. Swiss-albino mice were divided into two groups: 1. Control, 2. TRP-treated (100 mg/kg/24 h, i.p., for 7 days). Body weights were recorded at the beginning and at the end of experiments. Acetylcholine-induced contractile responses in the isolated ileum were recorded on polygraph. Ileal tissue malondialdehyde and glutathione levels determined by spectrophotometric and ileal tissue 5-HT levels were measured by immunohistochemical methods. TRP treatment decreased body weight and increased ileal contractile response. In the TRP-treated group, ileum malondialdehyde levels increased and glutathione levels decreased. Immunohistochemical detection showed that ileal 5-HT levels were increased by TRP treatment. There is a relationship between increased oxidative stress and increased contractility in the ileal tissue of the TRP-treated animals. These effects may be related to increased ileal 5-HT synthesis.

Enhancement effects of nicotine on neurogenic relaxation responses in the corpus cavernosum in rabbits: the role of nicotinic acetylcholine receptor subtypes.

Nicotine acts as an agonist of nicotinic acetylcholine receptors, which belong to a superfamily of neurotransmitter-gated ion channels. We previously demonstrated that nicotine increases the electrical field stimulation (EFS)-evoked nitrergic relaxation responses via activation of nicotinic acetylcholine receptors. The aim of the present study is to investigate the subtypes of nicotinic acetylcholine receptors in rabbit corpus cavernosum. EFS-evoked relaxation responses were recorded from corpus cavernosum strips obtained from rabbits with an isometric force displacement transducers. Effects of nicotine on EFS-evoked relaxations were examined in pre-contracted tissues. Then the effect of nicotine on the EFS-evoked relaxations was examined in the presence of hexamethonium, dihydro-beta-erythroidine, mecamylamine or alpha-bungarotoxin. In our study, nicotine (3 x 10(-5), 10(-4)) transiently increased nitrergic relaxations induced by EFS in the rabbit isolated corpus cavernosum. While hexamethonium and mecamylamine near totally inhibited or abolished the neurorelaxation response to nicotine (3 x 10(-5)) on EFS, dihydro-beta-erythroidine and alpha-bungarotoxin partially inhibited these responses. These findings demonstrated that the alpha3-beta4, alpha4-beta2 and alpha7 subunits of nicotinic acetylcholine receptors play role on the nicotine-induced augmentation in EFS-evoked relaxation responses in rabbit corpus cavernosum.

Role of nicotinic acetylcholine receptor subtypes on nicotine-induced neurogenic contractile response alternation in the rabbit gastric fundus

Nicotine is a nonspecific agonist of nicotinic acetylcholine receptors. We previously demonstrated that nicotine increases the electrical field stimulation (EFS)-evoked contractile responses possibly by facilitating neurotransmitters release from nerve terminals by a mechanism dependent on the influx of Ca(2+) from voltage gated Ca(2+) channels via activation of nicotinic acetylcholine receptor. The aim of this study is to investigate subtypes of presynaptic nicotinic acetylcholine receptors involved in nicotine induced EFS-evoked contractile response alternation in the rabbit gastric fundus. EFS-evoked contractile responses were recorded from gastric fundus strips obtained from rabbits with isometric force displacement transducers. Effects of nicotine on EFS evoked contractions were examined. Then the effect of nicotine on the EFS-evoked contractions was examined in the presence of hexamethonium, dihydro-beta-erythroidine, mecamylamine or alpha-bungarotoxin. In our study, nicotine (10(-4), 3x10(-4) M) transiently increased neurogenic contraction induced by EFS in the rabbit isolated gastric fundus. While hexamethonium, dihydro-beta-erythroidine and mecamylamine inhibited the neurocontractile response to nicotine on EFS, alpha-bungarotoxin did not alter these responses. The pA(2) values of the antagonists were 4.67 (hexamethonium, n=8), 5.33 (dihydro-beta-erythroidine, n=8) and 5.43 (mecamylamine, n=8). These findings showed that the alpha3beta4 and alpha4beta2 subunits of nicotinic acetylcholine receptors play a role on the nicotine-induced augmentation in EFS-evoked contractile responses in rabbit gastric fundus.

The effect of systemic leptin administration on aorta smooth muscle responses in diabetic rats.

Leptin produces effects in central nervous system and peripheral tissues via its specific receptors. Leptin also stimulates nitric oxide release in a concentration-dependent manner. In this study, our aim was to test the hypothesis that whether leptin has a modulatory role on endothelium or smooth muscle function in streptozotocin (STZ)-induced diabetic rats. Wistar-Albino rats were divided into four groups: 1 – Control, 2 – Diabetic, 3 – Control + leptin and 4 – Diabetic + leptin. Experimental diabetes was produced by intraperitoneal injection of a single dose of STZ (55 mg/kg). Diabetes was determined by increased fasting blood glucose level on the 7th day of the experiment. Leptin (0.1 mg/kg/day) was administered intraperitoneally for 5 days. At the end of the 5th day, thoracic aortas were isolated and phenylephrine (Phe)-induced contractions and acetylcholine (ACh)-induced relaxations of each group were estimated. In diabetic rats, Phe-induced contractility was increased (p < 0.05). Leptin pre-treatment increased the Phe-induced contractility significantly in aortic rings obtained from diabetic rats (p < 0.05). In normal rats, leptin administration produced only a slight and non-significant increase in Phe-induced contractions. Although the relaxant responses were decreased in diabetic rats, leptin administration enhanced the ACh-induced relaxation in both normal and diabetic animals significantly. As a conclusion; chronic leptin pre-treatment caused a significant increase both in Phe-induced contractions and ACh-induced Endothelial-Derived Relaxing Factor (EDRF)/Nitric oxide-mediated relaxations in the aortic rings isolated from streptozotocin-induced diabetic rats. This peptide hormone caused a significant increase in the relaxations obtained by ACh while not inducing a significant alteration in the contractile effect of Phe in control rats.

Prevention by a carbacyclin analogue (ZK 36 374) of digoxin-induced ventricular extrasystoles in guinea-pig myocardium☆

Intravenous infusion of ZK 36 374 to the anesthetized guinea-pig or addition of the compound to the perfusion medium of the isolated perfused guinea-pig heart prevented digoxin-induced ventricular premature beats without altering the prolongation of the P-R interval by the glycoside. The prevention by ZK 36 374 of the ventricular extrasystoles induced by digoxin was obtained at lower concentrations while higher doses of the compound produced a dysrhythmic effect which terminated within a few min after the cessation of drug application.

Hydrogen peroxide and antioxidizing enzymes involved in modulation of transient facilitatory effects of nicotine on neurogenic contractile responses in rat gastric fundus

Nicotine acts as an agonist of nicotinic acetylcholine receptors. Nicotinic acetylcholine receptors play a role in the modulation of neurotransmitter release in both the central and the peripheral nervous system. Moderate reactive oxygen species levels modulate the regulation of physiological functions e.g. neurotransmitter release. Previously in rabbit gastric fundus we demonstrated that nicotine transiently increased neurogenic contraction induced by electrical field stimulation (EFS). In this study we aimed to investigate the effects of hydrogen peroxide (H2O2), antioxidizing enzymes catalase and superoxide dismutase (SOD) on nicotine induced increases at cholinergic neurotransmission in rabbit gastric fundus. Although H2O2 did not alter nicotine induced transient neurogenic contractions at concentrations of 10(-6) and 10(-5) M, at high concentration (10(-4) M) H2O2 inhibited nicotine induced increases. Catalase (500 units/ml), enhanced the effect of nicotine but did not alter nicotine induced transient neurogenic contractions at the concentrations of 100 and 250 units/ml. SOD (75,150 and 225 units/ml) did not alter nicotine induced transient neurogenic contractions. In conclusion, at high concentration H2O2 (10(-4) M) inhibited nicotines transient ability to augment neurogenic contractions and catalase (500 units/ml) enhanced the effect of nicotine.

Does Thromboxane A2 Synthase Inhibitor UK-38485 Prevent the Vasoconstrictor Effects of Endothelin-1 on Rabbit Basilar Artery?

2 -a potent vasoconstrictor and aggregating metabolite of arachidonic acid- or infusion of the stable analogues of prostacyclin -which is another cyclo-oxygenase metabolite of arachidonic acid- has been shown to be beneficial in cerebral vasoconstriction. Endothelin-1, a peptide derived from endothelial cells, has been shown to induce a long-lasting cerebral vasoconstriction both in vivo and in vitro. The purpose of this study was to investigate the role of a novel thromboxane A2-synthase inhibitor UK 38485 on the acute vascular and morphological effects of Endothelin-1 applied intra-arterially on rabbit basilar arteries. The inguinal region of twenty four anaesthetized albino rabbits of both sexes were dissected and a catheter was inserted into the aorta via the femoral artery, for control angiography of the basilar artery and intra-arterial injection of ET-1 (0.25 ng total dose) and UK 38485 at a dose of 0.05 μg kg−1 min−1 for 20 min or saline. Angiographic vasoconstriction quantification and morphological investigations of both vessels and brain stem either by light microscopy or transmission electron microscopy were the techniques applied for the study. We found out that, although the systemic administration of UK 38485 resulted in a potent antagonism of the acute vasoconstriction as visualized in angiographic studies, it did not affect the morphological changes induced by Endothelin-1 on the vessel wall. The results indicated that there might have been an interaction between Endothelin-1 and the prostaglandin synthesis mechanism in acute cerebral vasoconstriction.