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    The cardiovascular system and the biochemistry of grafts used in heart surgery
    (Springer International Publishing Ag, 2013) Aydin, Suna; Aydin, Suleyman; Eren, Mehmet Nesimi; Sahin, Ibrahim; Yilmaz, Musa; Kalayci, Mehmet; Gungor, Orhan
    Blood is pumped into the cardiac muscle through arteries called the coronary arteries. Over time, the accumulation of cholesterol, coagulation factors, and cells on the walls of these arteries causes the walls to thicken and lose their elasticity, resulting in the development of atherosclerosis. When the blood supply of the heart is diminished by atherosclerosis, it can be restored by bypass surgery, in which atherosclerosis-free vein and/ or artery grafts taken from another area of the body are used to replace the atherosclerotic vessels. These biological grafts used in surgery differ in biochemical composition and long-term patency. Although the great saphenous vein (GSV) has been the most popular graft material in revascularization for years, it has recently been superseded by the internal mammarian artery (IMA), which has a lower incidence of recurrence of atherosclerosis. The aim of the present review is briefly to address the structure of the cardiovascular system and blood vessels, and then, in the light recent data, to present the biochemical compositions and individual advantages of the graft materials used to restore an impaired blood supply to the heart.
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    The dependence of tool overhang on surface quality and tool wear in the turning process
    (Springer London Ltd, 2010) Kiyak, Murat; Kaner, Billur; Sahin, Ibrahim; Aldemir, Bilal; Cakir, Orhan
    In the turning process, the importance of machining parameter choice is increased, as it controls the surface quality required. Tool overhang is a cutting tool parameter that has not been investigated in as much detail as some of the better known ones. It is appropriate to keep the tool overhang as short as possible; however, a longer tool overhang may be required depending on the geometry of the workpiece and when using the hole-turning process in particular. In this study, we investigate the effects of changes in the tool overhang in the external turning process on both the surface quality of the workpiece and tool wear. For this purpose, we used workpieces of AISI 1050 material with diameters of 20, 30, and 40 mm; and the surface roughness of the workpiece and tool wear were determined through experiments using constant cutting speed and feed rates with different depth of cuts (DOCs) and tool overhangs. We observed that the effect of the DOC on the surface roughness is negligible, but tool overhang is more important. The deflection of the cutting tool increases with tool overhang. Two different analytical methods were compared to determine the dependence of tool deflection on the tool overhang. Also, the real tool deflection values were determined using a comparator. We observed that the tool deflection values were quite compatible with the tool deflection results obtained using the second analytical method.
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    Examination of the tissue ghrelin expression of rats with diet-induced obesity using radioimmunoassay and immunohistochemical methods
    (Springer, 2012) Aydin, Suleyman; Sahin, Ibrahim; Ozkan, Yusuf; Dag, Ersel; Gunay, Ahmet; Guzel, Saadet Pilten; Catak, Zekiye
    Currently, obesity is an important health problem in all countries, both developed and developing. Dietary habits and neurohormonal imbalances play a critical role in obesity. Circulating amounts of ghrelin, which is a neurohormonal hormone, decrease with obesity and increase with weight loss. Although it is known that both mRNA and peptide version of the ghrelin hormone are expressed in almost all tissues of both humans and animals, it is not known how obesity changes the expression of this hormone in the tissues, with the exception of the gastrointestinal system tissues. Therefore, the objective of the present study is to show how diet-induced obesity in rats changes ghrelin expression in all system tissues, and thus, to shed light on the etiopathology of obesity. The study included 12 male and 12 female 2-month-old Wistar albino species rats. The animals in the control group were fed on standard rat pellet, while those in the experiment group were fed ad libitum on a cafeteria-style diet for 2 months. When their body mass index reached 1 g/cm(2), diet-induced obese (DIO) rats were sacrificed in a sterile environment after one night fasting. Ghrelin localizations in the tissues were studied immunohistochemically using avidin-biotin-peroxidase complex (ABC) method, while tissue ghrelin amounts were analyzed using radioimmunoassay (RIA) method. When the ghrelin amounts in the urogenital system (with the exception of kidney tissues), sensory organs, respiratory system, immune system, skeletal muscle system, cardiovascular system, nervous system, and adipose tissue of rats analyzed by RIA method were compared to those in the control group, tissue ghrelin amounts in the DIO group were found lower. Immunohistochemical findings which showed a similar fall in ghrelin concentrations in the tissues were parallel to RIA results. In addition, ghrelin was shown to be synthesized in the cardiovascular system, heart muscle cells, tails of the sperms, hair follicles, lacrimal glands, tongue, and teeth of rats for the first time in this study and ghrelin syntheses in these tissues were found to decrease in obesity. Nutritional obesity is among the most common causes of obesity and the findings we have obtained through diet-induced obesity will contribute to the illumination of the etiopathology of obesity.
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    Expression of adropin in rat brain, cerebellum, kidneys, heart, liver, and pancreas in streptozotocin-induced diabetes
    (Springer, 2013) Aydin, Suleyman; Kuloglu, Tuncay; Aydin, Suna; Eren, Mehmet Nesimi; Yilmaz, Musa; Kalayci, Mehmet; Sahin, Ibrahim
    We have investigated how diabetes affects the expression of adropin (ADR) in rat brain, cerebellum, kidneys, heart, liver, and pancreas tissues. The rats in the diabetic group were administered an intraperitoneal (i.p.) injection of a single dose of 60 mg/kg streptozotocin (STZ) dissolved in a 0.1 M phosphate-citrate buffer (pH 4.5). The rats were maintained in standard laboratory conditions in a temperature between 21 and 23 A degrees C and a relative humidity of 70 %, under a 12-h light/dark cycle. The animals were fed a standard commercial pellet diet. After 10 weeks, the animals were sacrified. ADR concentrations in the serum and tissue supernatants were measured by ELISA, and immunohistochemical staining was used to follow the expression of the hormones in the brain, cerebellum, kidneys, heart, liver, and pancreas tissues. The quantities were then compared. Increased ADR immunoreaction was seen in the brain, cerebellum, kidneys, heart, liver, and pancreas in the diabetes-induced rats compared to control subjects. ADR was detected in the brain (vascular area, pia mater, neuroglial cell, and neurons), cerebellum (neuroglial cells, Purkinje cells, vascular areas, and granular layer), kidneys (glomerulus, peritubular interstitial cells, and peritubular capillary endothelial cells), heart (endocardium, myocardium, and epicardium), liver (sinusoidal cells), and pancreas (serous acini). Its concentrations (based on mg/wet weight tissues) in these tissues were measured by using ELISA showed that the levels of ADR were higher in the diabetic rats compared to the control rats. Tissue ADR levels based on mg/wet weight tissues were as follows: Pancreas > liver > kidney > heart > brain > cerebellar tissues. Evidence is presented that shows ADR is expressed in various tissues in the rats and its levels increased in STZ-induced diabetes; however, this effect on the pathophysiology of the disorder remains to be understood.
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    Irisin: A potentially candidate marker for myocardial infarction
    (Elsevier Science Inc, 2014) Kuloglu, Tuncay; Aydin, Suna; Eren, Mehmet Nesimi; Yilmaz, Musa; Sahin, Ibrahim; Kalayci, Mehmet; Sarman, Emine
    Myocardial infarction (MI) causes energy depletion through imbalance between coronary blood supply and myocardial demand. Irisin produced by the heart reduces ATP production by increasing heat generation. Energy depletion affects irisin concentration in circulation and cardiac tissues, suggesting an association with MI. We examined: (1) irisin expression immunohistochemically in rat heart, skeletal muscle, kidney and liver in isoproterenol (ISO)-induced MI, and (2) serum irisin concentration by ELISA. Rats were randomly allocated into 6 groups (n=6), (i) control, (ii) ISO (1 h), (iii) ISO (2 h), (iv) ISO (4 h), (v) ISO (6 h), and (vi) ISO (24 h), 200 mg ISO in each case. Rats were decapitated and the blood and tissues collected for irisin analysis. Blood was centrifuged at 1792 g for 5 min. Tissues were washed with saline and fixed in 10% formalin for histology. Serum irisin levels gradually decreased from 1 h to 24h in MI rats compared with controls, the minimum being at 2 h, increasing again after 6 h. Cardiac muscle cells, glomerular, peritubular renal cortical interstitial cells, hepatocytes and liver sinusoidal cells and perimysium, endomysium and nucleoi of skeletal muscle were irisin positive, but its synthesis decreased 1-4 h after MI. At all time-points, irisin increased near myocardial connective tissue, with production in skeletal muscle, liver and kidney recovering after 6 h, although slower than controls. Unique insight into the pathogenesis of MI is shown, and the gradually decrease of serum irisin might be a diagnostic marker for MI. (C) 2014 Elsevier Inc. All rights reserved.
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    The Role of Apelins in the Physiology of the Heart
    (Bentham Science Publ Ltd, 2014) Aydin, Suna; Eren, Mehmet Nesimi; Sahin, Ibrahim; Aydin, Suleyman
    Apelins are a peptide hormone known as the ligand for the G protein-coupled APJ receptor. There are many different forms of apelin in the circulation. Apelins and their receptors are expressed in the central nervous system, including the hypothalamus, and in numerous other peripheral tissues. These peptides are also synthesized in and secreted from the adipose tissues. Additionally, apelins were immunohistochemically shown to be synthesized in smooth muscle cells in the media of the left internal mammary artery (LIMA) and the saphenous vein, fibroblast cells in the media of the aorta and endothelial cells of the intima. Similarly, it was recently reported that the enzyme linked immunoassay (ELISA) measurements of apelins were similar to its immunohistochemical data in the tissues of the aorta and left internal mammary artery. Apelins which are rapidly eliminated from the circulation have a half life of less than eight minutes. The normal concentration of apelins in the human plasma ranges between 1.3 ng/mL and 246 +/- 0.045 ng/mL. Apelins serve important functions in food intake, vasopressin (anti-diuretic hormone: ADH) and histamine release, gastric acid, bicarbonate secretion and insulin secretion, diuresis, cell proliferation, angiogenesis, glucose-fluid balance and regulation of gastrointestinal motility and cardiovascular system. Therefore, this review aims to focus on the potential role of the apelin system in the balance of the cardiovascular system.