Biomedical subjects
Publications and source records attributed to B Yilmaz.
A method for numerical simulation of two-term exponentially correlated colored noise is proposed. The method is an extension of traditional method for one-term exponentially correlated colored noise. The validity of the algorithm is tested by comparing numerical simulations with analytical results in two physical applications.
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The current study was designed to evaluate whether increased nuchal translucency can predict gestational diabetes mellitus. This was a prospective observational study. Among the pregnant women at 11-14 weeks of pregnancy who came to our prenatal unit for a first trimester screening test, 389 pregnant women whose nuchal translucency above 95th centile were selected as the study group and 386 age-matched pregnant women whose nuchal translucency were within the normal range were enrolled as a control group. First, subjects underwent a 50 g glucose screening test; if it was positive then a 100 g oral glucose tolerance test was performed. The main outcome measures were the prevalence of gestational diabetes mellitus and impaired glucose tolerance and the number of macrosomic infants. Impaired glucose tolerance was more common in pregnant women whose nuchal translucency was above the 95th centile (p = 0.048). In addition, macrosomic infants were also more common in pregnant women with a fetal nuchal translucency above the 95th centile (p = 0.045). Macrosomia was more common in the study group with gestational diabetes mellitus (p = 0.046). In conclusion, increased nuchal translucency seems to be predictive for impaired glucose tolerance and macrosomia, which are associated with gestational diabetes mellitus.
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INTRODUCTION: The aim of this study was to investigate the effects of dimethyl sulfoxide on liver damage caused by ischemia-reperfusion after portal vein clamping. MATERIAL AND METHODS: Forty New Zealand rabbits were divided into three groups with the portal veins of all the rabbits except the sham group clamped for 30 minutes: group I, sham procedure; group II, control group; and group III, 500 mg/kg DMSO. The drug was administered IM in the left inguinal region 30 minutes before the operation. Blood samples (5 mL) were taken from the animals at 15, 30, and 45 minutes. At the end of the experiment 1 g of liver tissue samples were obtained. Malondialdhyde (MDA), nitric oxide (NO), AST, ALT, and LDH plasma levels were measured in the blood samples. Liver tissue samples stained with hematoxylin eosin were examined under light microscopy for histopathological changes. FINDING: The liver enzymes in both clamping groups increased significantly compared with the sham group (P < .01). Enzyme levels of the DMSO group decreased significantly compared to the control clamping group (P < .05). Similar to the enzyme changes, MDA and NO levels increased in the portal vein clamping versus the sham group and decreased in the drug-administered group versus the control clamped group (P < .03). The severity of histopathological changes was less in the DMSO group than in the clamped controls. CONCLUSION: DMSO decreased the severity of liver damage after portal vein clamping.
Melatonin, the main hormone of the pineal gland, informs the body about the environmental light and darkness regimen, which in turn contributes to the photoperiodic adaptation of several physiological functions. Leptin, the hormone secreted mainly by adipocytes and some other tissues including the pituitary, informs the brain about the mass of adipose tissue, which plays an important role in energy homeostasis. Melatonin has been shown to decrease circulating leptin levels. It is currently not known whether melatonin has an effect on leptin synthesis in the pituitary. The aim of this study was to immunohistochemically examine the effects of pinealectomy and administration of melatonin on leptin production in the rat anterior pituitary. The pituitary samples obtained from 18 male Wistar rats including sham-pinealectomized, pinealectomized and melatonin-injected pinealectomized groups were immunohistochemically evaluated. Immunostaining of leptin was moderate (3+) in sham-pinealectomized rats, heavy (5+) in pinealectomized rats and low (1+) in melatonin-treated pinealectomized rats, respectively. The present results indicate that pinealectomy induces leptin secretion in anterior pituitary cells, and this increase of leptin synthesis can be prevented by administration of melatonin. Thus, melatonin seems to have both physiological and pharmacological effects on leptin production in the anterior pituitary of male rats.
Controversy still exists concerning the diagnosis and treatment of congenital lobar emphysema (CLE). Although surgical removal of the affected lobe is the most commonly accepted form of treatment, detection of milder or even asymptomatic cases is usually followed by a more conservative management of patients, i. e. non-surgical treatment and follow-up. We therefore decided to evaluate our patients with CLE, placing special emphasis on treatment and diagnostic techniques. We also evaluated quantitative analyses of alveolar diameters. Fourteen children with CLE were analysed retrospectively, including age, sex, clinical picture, localisation, diagnostic and surgical modalities and histopathologic diagnosis. The alveolar diameters of affected lobes were compared with those of the lobectomised patients with other non-obstructive respiratory diseases. All children but one had severe respiratory distress as an initial symptom. All patients, except newborns, had a history of pulmonary infection. All cases underwent thoracic CT examination as the main radiologic method. In all of the patients, only one lobe was affected. We found an obvious mediastinal shift and atelectasis of adjacent lobes due to compression of the affected lobe. The affected lobe was therefore surgically removed in all of the children. In one case, we had to carry out a partial lobectomy to reduce the duration of the operation, due to an intraoperative fall of oxygen saturation. All of the children had an uneventful clinical course postoperatively. The alveolar diameters of the cases with CLE were significantly greater than those of the control patients. We think that the majority of cases with CLE have too severe respiratory distress to avoid surgical removal of affected lobe. Conservative management should be reserved only for patients with milder symptoms or no distress at all.
1. This study was conducted to examine some egg characteristics and determine the effects of eggshell thickness and eggshell porosity on water loss and hatchability of eggs in ostriches. 2. Shell thickness did not correlate significantly with hatchability. However, eggs of low shell thickness lost more mass (13.03%) than those with intermediate (11.22%) and high (10.36%) shell thickness. Mass loss during incubation was higher in hatched (11.98%) than unhatched eggs (11.09%). Shell thickness was negatively correlated to egg mass loss (r = -0.65). 3. The pore density was correlated with hatchability. Hatchability was 50% lower in eggs with low pore densities (40.93%) than with high densities (80.94%). Pore density was positively correlated with egg mass loss (r = 0.63). Incubation mass losses of hatched and unhatched eggs were not significantly different. 4. Mean eggshell water vapour conductance (G) value and shell conductance constant (k) were 87.77 +/- 4.21 mg H2O/d/Torr and 2.44 respectively (n = 15). 5. Because of eggshell functional properties and resulting low egg mass loss hatchability is low when ostrich eggs are artificially incubated. The mass of eggs used in the experiment was relatively high and their eggshell water vapour conductance was low. As a result, egg incubation mass loss was lower than it should be. It is concluded that incubator humidity should be low (25%) to allow enough mass loss during incubation from the eggs.
The effects of pinealectomy and exogenous melatonin (N-acetyl-5-methoxytryptamine) on serum leptin levels were investigated in rats. Exogenous administration of melatonin to intact rats resulted in significant decreases in serum leptin levels (P < 0.05) compared to those of the intact control group. Serum leptin levels were significantly elevated in the pinealectomised rats in comparison to the sham-pinealectomised animals (P < 0.001) and were significantly suppressed by exogenous administration of melatonin compared to those of non-treated pinealectomised rats (P < 0.001). Hormone concentrations in the melatonin-treated pinealectomised group were found to be similar to those seen in the sham-pinealectomised group. These results suggest that pineal gland has an effect on leptin release.
Despite many years of study, certain aspects of myocardial ischemia remain incompletely understood. One observation that motivated this study is that acute, complete occlusion produces elevations but never depression of the ST-segment potentials in electrocardiographic leads over the ischemic zone. Limited flow, on the other hand, leads to ST-segment depression, both in in situ experiments and during clinical stress tests. The prevailing biophysical theory of ischemia suggests that complete occlusion should produce at least transient ST-segment depression, a finding we have neither observed in our own studies nor uncovered in the literature. Our goal with these experiments was to understand the difference between complete occlusion and reduced coronary flow, specifically the behavior at the transition between the two. We have performed experiments by using isolated dog hearts with a cannulated left anterior descending artery suspended in a human shaped electrolytic tank. To create a range of ischemic conditions, we changed coronary flow rates both suddenly and in controlled sequences and varied the heart rate of the isolated heart. The main finding was that in the isolated heart preparation, epicardial ST-segment depression over the ischemic zone arose only under conditions of combined restricted flow and elevated heart rate. Reduced coronary flow alone never produced ST-segment depression. These findings suggest that heart rate and probably metabolic work create the conditions necessary for subendocardial ischemia that reduced flow alone cannot provoke. They furthermore suggest that the degree of ST-segment depression for a given restriction in coronary flow may depend on heart rate, which supports the notion of rate correction for clinical stress electrocardiogram testing.
We have investigated the effects of thinner inhalation on serum LH, FSH and testosterone levels together with changes in hypothalamic catecholaminergic system in the male rat. A control group inhaled normal air ventilation. The remaining animals were divided into two groups and exposed to paint thinner in a glassy cage for 15 or 30 d. Toluene concentration (the largest constituent in thinner, 66%) was set at 3000 ppm in the inhalation air. At the end, all animals were decapitated and blood samples obtained. Serum LH and FSH levels were measured by RIA and testosterone by enzyme immunoassay. Following removal of brains on dry ice, medial preoptic area, suprachiasmatic nucleus, median eminence and arcuate nucleus were isolated by micropunch technique. Noradrenaline, 3,4-dihydroxyphenylglycol (DHPG) and dopamine concentrations of these hypothalamic areas were determined by HPLC-ECD. Fifteen-day thinner inhalation significantly suppressed serum LH and testosterone levels in parallel (p<0.001) compared to control group values (LH: 0.77+/-0.07; testosterone: 2.67+/-0.39). Thirty-day exposure markedly decreased LH levels (p<0.001), but surprisingly had no significant effect on testosterone. Serum FSH levels were not significantly altered in either group. Thinner inhalation for 15 or 30 d did not cause any significant change in noradrenaline, DHPG or dopamine concentrations in the hypothalamic regions examined (except in the arcuate nucleus). These results suggest that paint thinner has an anti-gonadotropic effect and may cause long-term endocrine disturbances in the male. It is thought that the hypothalamic catecholaminergic system is not involved in thinner inhibition of LH and testosterone secretion.
OBJECTIVE: The aim of this study was to investigate the effects of melatonin on spontaneous and oxytocin-induced contractility of pregnant and non-pregnant rat myometrium in vitro. DESIGN: Myometrial strips were removed from virgin or late pregnant (21 days gestation) Wistar rats following decapitation and placed in an organ bath containing Krebs' solution at 37 degrees C and pH 7.4, constantly bubbled with 95% oxygen-5% carbon dioxide and isometric contractions were recorded. Effects of cumulative concentrations of melatonin (0.1 to 10 microM) on spontaneous and oxytocin-induced contractions were studied. Possible involvement of Ca(2+)-activated K (+) channels in inhibitory actions of melatonin was investigated by using apamin (100 nM). RESULTS: Melatonin inhibited spontaneous and oxytocin-induced contractions of myometrium from both virgin and late pregnant rats in a dose-dependent manner. After inhibition of oxytocin-induced contractions by melatonin, application of prostaglandin F (2alpha) (1 microM) but not high KCl (30 mM) containing solution initiated contractile activity. Inhibitory response induced by melatonin (13 microM) was not affected by apamin (100 nM). CONCLUSIONS: Data from this study demonstrates that melatonin inhibits spontaneous and oxytocin-induced contractions of myometrium from pregnant and non-pregnant rats. Although the exact mechanism is not clear, melatonin-induced inhibition of myometrial contractions may results from its interactions with Ca(2+) channels.
We have investigated the role of mu- and kappa-opioid receptors in the central control of preovulatory LH and FSH release in the proestrous rat. Animals were anesthetized with chloral hydrate at 14:00 h on proestrus day. Following femoral artery cannulation, they were mounted in a stereotaxic apparatus. Morphine and U-50488H (benzene-acetamide methane sulphonate) were infused intracerebroventricularly either alone or in combination with naloxone and MR1452, respectively. Controls received sterile saline alone. Blood samples were obtained at hourly intervals between 15:00 h and 17:00 h. Plasma LH and FSH levels were measured by radioimmunoassay. Morphine did not significantly change plasma LH levels at 15:00 h and 16:00 h sampling intervals. A significant increase was observed at 17:00 h compared to the controls (p<0.05). U-50488H significantly increased LH levels at 16:00 h and 17:00 h (p<0.05). The co-administration of naloxone and MR1452 with mu- and kappa-agonist had no significant effect on LH levels at any sampling interval. In all groups, LH levels showed a linear rise over the sampling period between 15:00 h and 17:00 h. None of the treatments significantly altered plasma FSH levels which however, declined towards the end of the afternoon surge. In conclusion, we suggest that the secretion of LH and FSH is differentially regulated by mu- and kappa-opioid receptors. It is thought that in all groups chloral hydrate interfered with the LH surge secretory systems.
Previous studies have examined the influence of body position, respiration, and habitus on body surface potentials. However, the authors could only estimate the sources of the effects they documented. Among the proposed origin of changes in body surface potentials from those studies were the position of the heart, alterations in autonomic tone, differences in ventricular blood volume, and variations in torso resistivity. The goal of this study was to investigate specifically the role of geometric factors in altering body surface potentials and the electrocardiogram. For this, we used experiments with an isolated, perfused dog heart suspended in a realistically shaped electrolytic torso tank. The experimental preparation allowed us to measure epicardial and tank surface potentials simultaneously, and then reconstruct the geometry of both surfaces. Our results mimicked some of the features described by previous investigators. However, our results also showed differences that included considerably larger changes in the peak QRS and T-wave amplitudes with heart movement than those reported in human studies. We detected smaller values of root-mean-squared variability from heart movements than those reported in a human study comparing body surface potentials during change in inspiration and body position. There was better agreement with relative variability, which in these studies ranged from 0.11 to 0.42, agreeing well with an estimate from human studies of 0.40. Our results suggest that the isolated heart/torso tank preparation is a valuable tool for investigating the effects of geometric variation. Furthermore, the geometric position of the heart appears to be a large source of variation in body surface potentials. The size of these variations easily exceeded thresholds used to distinguish pathologic conditions and thus such variations could have important implications on the interpretation of the standard electrocardiogram.
Although it is known that platelet count is altered in iron deficiency anaemia (IDA), the qualitative extent of this interference is not well documented. In the present study we investigated platelet aggregation (PA) by impedance and optic methods in IDA. Forty-seven patients (plasma group: 16 boys, 9 girls and whole blood group: 11 boys, 11 girls) with IDA and thirty-one healthy children (plasma group: 6 boys, 10 girls and whole blood group: 6 boys, 9 girls) were enrolled into the study. Template bleeding times were measured by the Ivy method in all children. In the control group whole blood count, serum iron levels, bleeding time and PA were determined. After basal PA was determined in the patients and controls, ferrous sulphate was orally administered to the patients at a dose of 6 mg/kg/24 h for three months. Then, PA tests were performed again in the IDA (test group) patients. Ristocetin-induced PA was suppressed in both plasma and whole blood groups. Inhibition by both collagen (p < 0.05) and ristocetin (p < 0.001)-induced PA was determined by the optic method. Similarly in PA measured by the impedance method a suppression to adenosine diphosphate (p < 0.001) and to ristocetin (p < 0.01) was found. However, no significant alteration was observed in the bleeding time. All defective responses were reversed by the iron supplementation therapy. In addition, a significant correlation was found between some parameters of PA and several haematological values. In conclusion, although defective PA responses cannot be clinically demonstrated in patients with IDA, this suppression of PA may be detected by laboratory examination. Therefore, it is advised that care should be taken when using anti-aggregant agents in IDA.
We have investigated the effects of specific mu-, kappa-and delta-opioid receptor agonists and antagonists on the hypothalamic noradrenergic neurotransmission and on luteinising hormone (LH) release in the ovariectomised and steroid-primed rat. The opioid agents were infused intracerebroventricularly under ketamine anaesthesia and blood samples collected at hourly intervals on the afternoon of the anticipated LH surge. At the end of the experiment, the rats were decapitated and the medial preoptic area, suprachiasmatic nucleus, median eminence and arcuate nucleus surgically isolated by micropunch. The concentrations of noradrenaline (NA) and its metabolite (3,4-dihydroxyphenylglycol; DHPG) in these samples was determined by high performance liquid chromatography with electrochemical detection. Plasma LH levels were measured by radioimmunassay. The three opioid agonists reduced concentrations of NA and DHPG in all four hypothalamic areas. These inhibitory effects of the opioid agonists were mostly prevented following coadministration with their respective antagonists. However, naloxone had no significant effect on DHPG levels in any of the hypothalamic regions examined. Plasma LH levels were found to be either low or undetectable in all groups. These results suggest that mu-, kappa- and delta-opioid receptors have inhibitory influence on the hypothalamic noradrenergic neurotransmission around the time of the LH surge. It is thought that the ketamine anaesthesia interfered with LH release.
Although disorders of ADH secretion associated with meningitis are usually consistent with the Syndrome of Inappropriate Antidiuretic Hormone Secretion (SIADH), central diabetes insipidus (DI) is an exceptional complication of meningitis. Transient DI as a complication of Escherichia coli (E. coli) meningitis due to ventriculoperitoneal shunt in an 18-month-old boy is presented. Blood and spinal fluid cultures yielded E. coli, sensitive to cefotaxime. The DI arose on the day 3 after admission and continued to the day 20. Treatment comprised cefotaxime, dexamethasone, fluid adjustment and vasopressin. The course of our case supports that in cases of bacterial meningitis, initial fluid restriction may occasionally result in dangerous conditions. Therefore, all children with bacterial meningitis should be followed closely not only in terms of SIADH but also DI. To our knowledge this is the first transient DI associated with E. coli-caused meningitis case reported.
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