Mehmet Şimşek

On the origin of the Bosphorus

Abstract The Palaeozoic-Upper Cretaceous basement palaeomorphology of the Bosphorus (the Strait of Istanbul) bears the evidence of a valley of a palaeostream running to the Black Sea in the north, a palaeobasin deeper than —160 m opening to the Sea of Marmara in the south, and a barrier between these two features. This suggest that the northern part of the Bosphorus was formed mainly by fluvial activity, whereas the southern part developed as a basin by faulting. The recent sediment thickness exceeds 130 m in the basin, indicating that the southern part of the Bosphorus was once essentially depositional rather than an erosional. The present form of the Bosphorus was established in Holocene time by the connection of the basin in the south with the stream in the north. The barrier and the stream valley in the north have been deepened by erosion and faulting to form a strait connecting the Black Sea and the Mediterranean.

The last sea level changes in the Black Sea: evidence from the seismic data

Abstract High resolution shallow seismic data collected from the southwestern shelf of the Black Sea indicate five different seismic stratigraphical units. The lower three of them belong to the Upper Cretaceous–Eocene, Oligocene–Miocene and Early Quaternary (prior to Holocene) sediments, respectively. These units are considered as a basement for the recent sediments deposited related to the latest connection of the Black Sea and the Mediterranean. The surface of these units are truncated to form an etchplain developed before the Flandrian transgression. The fourth unit covers the older units by an onlap. Its contact with the older units seen at −105 m is the shoreline of the Black Sea prior to the last major sea-level change. The fifth unit has been deposited since drowning of the Black Sea shelf. The principal cause of drowning of the Black Sea shelf is not only the last sea level rise as it is at the shelves of the Sea of Marmara but also the opening of the Strait of Istanbul. It is also realised by the comparison of the shelf area and the Catalca–Kocaeli etchplain that, the present continental part of this etchplain has been considerably uplifted with respect to the shelf area along the present shoreline. This uplifting must have also reactivated the faults around the Strait of Istanbul foundering the strait valley and, thus, permitting the Mediterranean waters to pass into the Black Sea, and initiating the sudden drowning of the Black Sea shelf.

Moderate exercise with a dietary vitamin C and E combination protects against streptozotocin-induced oxidative damage to the blood and improves fetal outcomes in pregnant rats

Abstract A considerable amount of clinical and experimental evidence now exists suggesting that many biochemical pathways strictly associated with diabetes increase the production of reactive oxygen species (ROS). However, daily moderate exercise and vitamins C and E(VCE ) supplementation can be beneficial to diabetes due to reducing blood glucose and free radical production. In the present study, we investigated the effect of VCE and moderate exercise on lipid peroxidation (MDA) and scavenging enzyme activity in the blood of STZ-induced diabetic pregnant rats. Fifty female Wistar rats were used and were randomly divided into five groups. The first and second were used as the control and pregnant control groups, respectively. The third group was the pregnant diabetic group. The fourth group was the diabetic-pregnant-exercise group. VCE-supplemented feed was given to pregnant-diabetic-exercise rats constituting the fifth group. Animals in the exercised groups were moderately exercised daily on a treadmill (16.1 m/min, 45 min/d) for three weeks (five days a week). Diabetes was induced on day zero of the study. Body weights in the five groups were recorded weekly. Plasma and red blood cell (RBC) samples were taken from all animals on day 20. Glutathione peroxidase (GSH-Px), catalase and reduced glutathione (GSH) levels in plasma and RBCs, glucose, vitamins A, E and β-carotene in plasma, the number of fetuses, and body weight were lower in pregnant diabetic rats than in control animals, whereas there was a significant increase in platelet counts and plasma and RBC MDA levels. The decreased antioxidant enzymes did not improve through exercise only. However, the decreased vitamins, and increased MDA, glucose levels and white blood cell (WBC) counts were improved either by exercise or exercise plus VCE supplementation. There were no significant changes in the RBC counts and hemoglobin values in the five groups. In conclusion, these data demonstrate that there is an increase in MDA in the blood of diabetic pregnant animals, whereas there is a decrease in the number of fetuses, antioxidant vitamins and enzymes. However, dietary VCE with moderate exercise may strengthen the antioxidant defense system due to reducing ROS. They may play a role in preventing diabetes-related diseases of pregnant subjects.

Impact of intracystic ethanol instillation on ovarian cyst diameter and adjacent ovarian tissue

OBJECTIVE To investigate the regression level of simple ovarian cyst size after local ethanol application and the damage level of adjacent ovarian reserve in rats. STUDY DESIGN This study was conducted at Firat University Animal Laboratory with 18 mature (12-14 weeks old) female Wistar albino rats weighing 200-220g, with regular cycles. Ovarian cyst induction was performed with unilateral salpingectomy. Fourteen rats with ovarian cysts after a second laparotomy were divided into two groups as follows: Group 1 (n=7): cyst aspiration group, and Group 2 (n=7): intracystic 95% ethanol application group. One month after the cyst aspiration procedure a third laparotomy was performed. The cyst number and size were recorded for each rat. Right ovariectomy was performed and formalin-fixed/paraffin-embedded tissues were sectioned at 5μm thickness. Under light microscopy, ovarian total follicle reserve and fibrosis were evaluated with Masson trichrome staining and apoptosis was evaluated with TUNEL staining. The groups were compared with the Mann-Whitney U test and Wilcoxon Rank test. p<0.05 was considered significant. RESULTS Ovarian cyst formation was observed in 85% (15/18) of rats. The mean diameter of ovarian cysts in Groups 1 and 2 were, respectively, 10.3mm and 10.1mm. After aspiration, there was no significant reduction in the cyst diameter (10.3mm vs 8.1mm), but after ethanol application the diameter significantly reduced (10.1mm vs 3.4mm, p<0.05). Mean ovarian follicle count in Group 2 was significantly lower than in Group 1 (25 vs 42, p<0.05), and mean fibrosis and apoptosis scores in Group 2 were significantly higher than in Group 1 (2.5 vs 0.9, p<0.05). CONCLUSION Local ethanol application reduces cyst diameter but concomitantly decreases ovarian reserve due to increased fibrosis in rats. In humans, intracystic ethanol application should be performed cautiously.

Our clinical experience about prenatal diagnosis and neonatal outcomes of fetal central nervous system anomalies.

Objective. To present a retrospective analysis of the prenatal diagnosis and the outcome of fetuses diagnosed with central nervous system (CNS) anomalies. Materials and methods. We reviewed the medical records and ultrasound data of 69 cases diagnosed with CNS anomalies from 2007 to 2008. We described the prenatal diagnosis, associated findings, and outcome of these patients. Results. Sixty-nine patients were diagnosed with CNS anomalies. Of these, 31 had ventriculomegaly + hydrocephaly, 14 had spina bifida + meningomyelosel, 5 had choroid plexus cyst, 5 had Dandy Walker malformation, 3 had sacrocoxigeal teratoma, 2 had encephalosel, 1 had microcephaly, and 1 had Arnold Chiari malformation. Eight amniocentesis, three cord blood sampling, and two fetal reduction procedure were performed. Nine pregnancy termination and 36 delivery were performed. Neurosurgical correction was performed for neonates with spina bifida, hydrocephaly and sacrocoxigeal teratoma. Twenty-one neonates were discharged with cure, 4 neonates with follow-up, 7 neonates with paraplegia, and 13 neonates died. Conclusion. The outcome of fetuses with CNS anomalies was shown to depend mainly on the degree of neural tube defect and the associated anomalies were the most important factors in surviving.

The effect of ethanol sclerotherapy of 5 minutes duration on cyst diameter and rat ovarian tissue in simple ovarian cysts

Objectives To examine the effect of 95% ethanol sclerotherapy (EST) administered over 5 minutes on cyst diameter and ovarian tissue in experimentally induced simple ovarian cysts in a rat model. Materials and methods In order to induce ovarian cysts, unilateral total salpingectomy was performed in regularly menstruating adult female Wistar albino rats (n=20) between 12 and 14 weeks of age and weighing between 200 and 220 g. One month after the procedure, the abdominal cavity was opened and 14 rats (70%) were found to have developed macroscopic cysts. Rats with macroscopic cysts (n=14) were assigned into two groups in a prospective and single-blinded manner: group 1 (G1) (n=7), control rats; and group 2 (G2) (n=7), 5-minute EST 95% group. Cyst diameter was measured and recorded for each rat. In G2, after whole cyst fluid was aspirated the cystic cavity was irrigated with 95% ethanol, approximately equal to half of the aspirated cyst volume, after which an interval of 5 minutes was allowed and same amount was re-aspirated and the abdominal cavity was closed. One month after this procedure, abdominal cavities were reopened and intra-abdominal adhesion scoring was performed in both groups. Cyst diameter was measured for each rat, and the right ovary was removed, fixed in 10% formaldehyde, and transported to the laboratory. A histologic assessment of the ovarian tissues was performed under light microscopy following staining with hematoxylin and eosin. Mann–Whitney U-test was used for statistical analysis. A P-level less than 0.05 was considered significant. Results In comparison with G1, there was a statistically significant reduction in the mean ovarian cyst dimensions in G2, while there were no significant differences between the two groups with respect to total number of follicles. Again, a significant increase in apoptotic activity and germinal epithelial degeneration was observed in G2 as compared to G1. The two groups were similar in terms of adhesion formation. Conclusion Although 95% EST results in a reduction in the size of simple ovarian cysts, this effect seems to be achieved at the expense of ovarian tissue injury.