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Öğe Choice of smoothing parameter for kernel type ridge estimators in semiparametric regression models(National Statistical Institute, 2021) Yilmaz E.; Yuzbasi B.; Aydin D.This paper concerns kernel-type ridge estimators of parameters in a semiparametric model. These estimators are a generalization of the well-known Speckman’s approach based on kernel smoothing method. The most important factor in achieving this smoothing method is the selection of the smoothing parameter. In the literature, many selection criteria for comparing regression models have been produced. We will focus on six selection criterion improved version of Akaike information criterion (AICc), generalized cross-validation (GCV), Mallows’ Cp criterion, risk estimation using classical pilots (RECP), Bayes information criterion (BIC), and restricted maximum likelihood (REML). Real and simulated data sets are considered to illustrate the key ideas in the paper. Thus, suitable selection criterion are provided for optimum smoothing parameter selection. © 2021, National Statistical Institute. All rights reserved.Öğe Prevention of Fertility due to Chemotherapy-Induced Ovarian Failure: Role of Therapeutic Antioxidants(Springer Singapore, 2022) Melekoglu R.; Dogan U.K.; Celik N.Z.; Yilmaz E.Advancements in chemotherapy treatments are leading to increased survival rates for cancer sufferers. Advances in anticancer therapy have contributed to higher survival rates, but ovarian failure that leads to infertility is one of the long-term adverse effects due to primordial follicle loss caused by gonadotoxic chemotherapy. Therefore, prevention of premature ovarian failure and protection of the ovarian follicle pool has gained increasing attention to improve the quality of life of female cancer patients receiving chemotherapy. A non-invasive medical approach (including administration of antioxidant therapy to conventional chemotherapy regimens) to prevent chemotherapy-induced ovarian damage may be preferred, although there are successful invasive fertility preservation options. Most of the chemotherapeutic agents act by producing free radicals that cause cellular damage and necrosis of malignant cells as part of their mode of action in cancer treatment. Despite nearly three decades of research that sought to determine the effectiveness and safety of dietary antioxidant supplementation while undergoing conventional chemotherapy, some controversy remains about efficacy and safety. This claim has been backed up by numerous clinical trials which have demonstrated that certain antioxidants help to restore the body’s natural antioxidants, which are often depleted after chemotherapy treatment, and reduce side effects of cytotoxic agents, including prevention of chemotherapy-induced ovarian failure as well as increase in overall survival of patients receiving chemotherapy. Further randomized controlled clinical researches should be designed to evaluate the use of a specific combination of antioxidants in chemotherapy and determine optimal doses of antioxidants for specific cancer setting to prevent chemotherapy-induced ovarian failure. © Springer Nature Singapore Pte Ltd. 2022.Öğe Serum levels of apelin, salusin-alpha and salusin-beta in normal pregnancy and preeclampsia(2012) Simsek Y.; Celik O.; Yilmaz E.; Karaer A.; Dogan C.; Aydin S.; Ozer A.Objective: The purpose of this study was to investigate the relationship between the serum apelin, salusin-alpha and salusin-beta levels and preeclampsia. Method: Twenty-one healthy pregnant women (control group) and 48 patients with preeclampsia (study group) were included in the study between August 2010 and February 2011. Serum apelin, salusin-alpha and salusin-beta levels of the groups were compared. Results: The patients in the study group were divided into two categories: mild preeclampsia and severe preeclampsia. The mild preeclampsia group consisted of 31 patients, and the severe preeclampsia group consisted of 17 patients. Serum salusin-alpha and salusin-beta levels of the control and study groups were not significantly different (p > 0.05). Apelin levels were statistically significantly higher in the study group. No statistically significant difference was detected between the mild and severe preeclampsia groups in terms of the mean serum apelin levels. Conclusion: The serum levels of apelin were higher in the pregnant women with preeclampsia; however, there was no positive relationship between serum salusin-alpha and salusin-beta levels and the disease. Larger prospective studies are needed to validate our findings. © 2012 Informa UK, Ltd.Öğe XPD and XRCC1 gene polymorphism in patients with normal and abnormal cervical cytology by pap smear.(2012) Yilmaz E.; Celik O.; Celik E.; Turkcuoglu I.; Simsek Y.; Karaer A.; Otlu B.The purpose of the present study was to identify the role of abnormalities in DNA repair pathways by measuring the XPD and XRCC1 gene polymorphisms. Thirty-five patients with abnormal cervical cytology (study group) and 10 women with normal cytology (control group) were included in the study. The polymorphisms of XRCC1 Arg194Trp, XRCC1 Arg399Gln and XPD Lys751Gln genes were investigated from the blood samples. There was no statistically significant difference in allele frequencies of XPD gene among the groups (p = 0.097), while XRCC1R399Q gene polymorphism was strikingly more frequent in the study group than that of control cases (p = 0.029). The prevalence of XRCC1R194W gene polymorphism on the other hand, was similar between the groups (p = 0.579). Patients with abnormal and normal cervical cytology have similar XPD gene polymorphism. However, the frequency of gene polymorphism in XRCC1 Arg 399 Gln codon was significantly higher in abnormal cervical cytology group.
