Ahmet Kalkan
Fırat University
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Publication
Featured researches published by Ahmet Kalkan.
Journal of Clinical Microbiology | 2006
Sukru Tonbak; Munir Aktas; Kursat Altay; Ahmet Kursat Azkur; Ahmet Kalkan; Yusuf Bolat; Nazir Dumanli; Aykut Ozdarendeli
ABSTRACT Crimean-Congo hemorrhagic fever virus (CCHFV) is a tick-borne virus in the family Bunyaviridae, genus Nairovirus. The virus is transmitted to humans through infected tick bites or from direct contact with viremic animals or humans. In the present study, a total of 1,015 adult ticks were collected from cattle (603 specimens), sheep (17 specimens), and goats (395 specimens) in the Kelkit Valley in Turkey. Four tick species were recognized on the animals in the surveyed region. The most abundant species were Rhipicephalus bursa and Hyalomma marginatum marginatum, at 47.68% (484/1,015) and 46.40% (471/1,015), respectively. Reverse transcriptase PCR was used to recover partial sequences of the CCHFV small (S) genome segment. The presence of CCHFV was determined in 3 of 33 (9.09%) R. bursa pools and in 1 of 31 (3.22%) H. m. marginatum pools. Virus sequences from R. bursa were extremely different from those of the Greek CCHFV strain (U04958) isolated from an R. bursa tick. Phylogenetic analysis indicated that the CCHFV isolates obtained in this study clustered in group 5, whose range encompasses southwestern Russian and Kosovo. This is the first evidence of CCHFV in ticks from Turkey. Even though Hyalomma is the main vector for CCHFV, R. bursa may play a role in CCHFV transmission.
Journal of Trace Elements in Medicine and Biology | 2002
Ahmet Kalkan; Vedat Bulut; Senel Avci; İlhami Çelik; Namik Kemal Bingol
In this study, serum trace elements, including selenium (Se), zinc (Zn), copper (Cu), were determined by using Atomic Absorption Spectrophotometer (SpectrAA 250 Plus Zeeman, Varian, Australia) in sera of patients with viral hepatitis (A, B, C, D, E) cases (n = 102), and statistically compared with the controls (n = 52). In viral hepatitis, Cu levels were found as 3.23 +/- 1.02 mg/L, and this value was significantly higher than the control group (1.13 +/- 0.21) (p < 0.01). Both, Se and Zn levels found to be significantly low in viral hepatitis cases (p < 0.01). While Se level was 81.4 +/- 26.01 microg/L in viral hepatitis (n = 101), it was found to be 166.15 +/- 4.58 microg/L in healthy individuals. Meanwhile, Zn levels were 0.230 +/- 0.081 mg/L and 0.748 +/- 0.392 mg/L in hepatitis cases (n = 101) and the control group, respectively. There was no difference amongst viral hepatitis groups classified in regard with agents and clinical manifestation, such as A, acute hepatitis B, chronic hepatitis B, C, D and E. Previously, it was indicated that absorption disorders in gastrointestinal system, especially in chronic cases, were not main causes of decrease of trace elements by iron and several other parameters in sera of the cases. Therefore, we suggest that decrease in Zn and Se levels and elevation in Cu levels are probably resulted from defence strategies of organism and induced by the hormone-like substances.
Journal of Gastroenterology and Hepatology | 2004
Kutbeddin Demirdag; Ibrahim Halil Bahcecioglu; Ibrahim Hanifi Ozercan; Mehmet Ozden; Seval Yilmaz; Ahmet Kalkan
Background and Aim: Lipid peroxidation is the most important mechanism in the pathogenesis of acute liver damage with carbon tetrachloride (CCl4). L‐carnitine may prevent lipid peroxidation and thus may protect against liver damage. In the present study we investigated the protective effect of L‐carnitine in experimental acute liver damage induced by CCl4.
Fems Immunology and Medical Microbiology | 2003
Kutbettin Demirdag; Mehmet Ozden; Ahmet Kalkan; Ahmet Godekmerdan; S. Sirri Kiliç
The number of clinical studies on gamma interferon (IFN-gamma), tumor necrosis factor-alpha (TNF-alpha) and interleukin-4 (IL-4) in human brucellosis is limited. The present study was focused on IFN-gamma, TNF-alpha and IL-4 levels in acute brucellosis cases, in the acute phase and at the end of the treatment. The relation of these cytokines to traditional inflammation markers was also investigated. The study included 27 cases of acute brucellosis and 20 healthy volunteers who had no complaints. It was found that mean IFN-gamma and TNF-alpha levels, CRP (C-reactive protein) levels and ESR (erythrocyte sedimentation rate) values were significantly higher in acute brucellosis cases as compared to post-treatment values and values measured in the control group. In addition, IFN-gamma and TNF-alpha levels measured in the acute phase correlated with the increase in CRP levels and ESR values. Our results confirmed that IFN-gamma and TNF-alpha are involved in the pathophysiology of brucellosis and are closely related to the inflammatory activation of the disease. In view of the present findings, it is suggested that IFN-gamma and TNFalpha may be used for monitoring brucellosis.
Parasitology Research | 2009
Munir Aktas; Kursat Altay; Nazir Dumanli; Ahmet Kalkan
A polymerase chain reaction (PCR) assay followed by partial sequencing of the 16S ribosomal RNA gene was performed for the presence of Ehrlichia and/or Anaplasma. A total of 242 ixodid ticks were collected from domestic ruminants and their shelters, as well as humans, and their individual salivary glands were dissected out for DNA. From the 242 ticks analyzed, six (2.47%), comprising three Hyalomma anatolicum anatolicum, one Rhipicephalus bursa, and two Rhipicephalus sanguineus, were positive. Of these sequenced samples directly obtained from the PCR products, three sequences from H. a. anatolicum were identical to that of the gene of Ehrlichia spp. strains. One sequence identified in R. bursa was closely related to Anaplasma platys. The remaining two sequences detected in R. sanguineus were similar to that of the gene of Anaplasma ovis. The study presented here provides preliminary data regarding the presence of rickettsial pathogens in ticks in Turkey.
Virus Research | 2010
Aykut Ozdarendeli; Nurettin Canakoglu; Engin Berber; Kemalettin Aydin; Şükrü Tonbak; Mustafa Ertek; Turan Buzgan; Yusuf Bolat; Munir Aktas; Ahmet Kalkan
Crimean-Congo hemorrhagic fever virus (CCHFV) is the causative agent of a tick-borne disease with high mortality rates in humans. The distribution of CCHFV includes over 30 countries in Asia, the Middle East, southeastern Europe, and Africa. It was first recognized in Turkey in 2002, with an increasing number of cases reported between 2002 and 2009. Recent analysis of complete genome sequences of CCHFV isolates has revealed that the genomic plasticity of the virus is surprisingly high for an arthropod-borne virus. We have determined the complete nucleotide and deduced amino acid sequences of strain CCHFV Turkey-Kelkit06 isolated from the blood of a patient in an endemic region of Turkey in 2006. The complete sequence length of the CCHFV Turkey-Kelkit06 strain is 19,186 nt, consisting of a 1673 nt S segment, a 5364 nt M segment, and a 12,149 nt L segment. Based on the analysis of S, M, and L segments, CCHFV Turkey-Kelkit06 clustered in Group V, which represents the Europe/Turkey geographic lineage. Although glycoproteins encoded by the M gene are the most variable part of the CCHFV Turkey-Kelkit06 strain, some functional domains of the glycoproteins are well conserved. Here, we report the complete sequence and genome organization of the CCHFV Turkey-Kelkit06 strain and its phylogenetic relationship to other strains of CCHFV. Collecting data on viral sequences among isolates from CCHF epidemics may provide valuable information regarding the molecular basis of the epidemic potential of the virus.
Archives of Virology | 2008
Aykut Ozdarendeli; Kemalettin Aydin; Sukru Tonbak; Munir Aktas; Kursat Altay; I. Koksal; Yusuf Bolat; Nazir Dumanli; Ahmet Kalkan
SummaryCrimean-Congo hemorrhagic fever (CCHF) virus is member of the genus Nairovirus of the family Bunyaviridae. All members of the family Bunyaviridae are enveloped viruses containing tripartite, negative polarity, single-stranded RNA. CCHF is characterized by high case mortality, occurring in Asia, Africa, the Middle East and Europe. During recent years, outbreaks have been reported in Turkey. However, little information is available on the genetic diversity of CCHF virus in Turkey. In this study, a total of 1227 adult ticks were collected from domestic ruminants (796 specimens from cattle, 399 specimens from goats and 32 specimens from sheep). The presence of the M segment of CCHF virus was determined in 4 of 40 (10%) Hyalomma marginatum marginatum pools, in 2 of 38 (7.89%) Rhipicephalus bursa pools, and in 1 of 7 (7%) Boophylus annulatus pools. Hyalomma anatolicum anatolicum pools gave negative RT-PCR result against CCHF virus. Serum samples from seven patients infected with CCHF were selected and subjected to RT-PCR to amplify partial M segment of CCHF virus. This report introduces the first data on partial nucleotide sequences of M RNA segments of CCHF virus strains circulating in Turkey, isolated from ticks.
Medical Principles and Practice | 2005
Ahmet Kalkan; Aykut Ozdarendeli; Yasemin Bulut; Hayrettin Yekeler; Bengu Cobanoglu; Mehmet Z. Doymaz
Objective: To investigate etiological role of Epstein-Barr virus (EBV) DNA in breast cancer. Materials and Methods: The presence of EBV DNA in 57 breast cancer tissues was investigated with a sensitive PCR assay. The breast cancer tissues were from invasive ductular (n = 28), lobular (n = 20) and other miscellaneous carcinomas (n = 9). Tissues from normal breasts and patients with various benign breast diseases (n = 55): fibrocystic disease (n = 34), fibroadenoma (n = 16), hyperplasia, and granulomatous mastitis (n = 5), were used as control samples. Results: EBV DNA was detected in 13 (23%) cancerous tissues (7 ductular, 4 lobular, 2 other carcinoma) and 19 (35%) in the control tissues. The difference between EBV presence in malignant and benign tissues was not statistically significant (p > 0.05). Conclusion: The presence of EBV DNA was detected almost equally in both breast cancer and normal tissues, which indicates no etiological role for EBV in breast cancer. We suggest further etiological studies.
Memorias Do Instituto Oswaldo Cruz | 2004
Mustafa Kaplan; Ahmet Kalkan; Salih Hosoglu; Salih Kuk; Mehmet Ozden; Kutbedtin Demirdag; Aykut Ozdarendeli
Human toxocariasis is commonly seen in places where stray and Toxocara canis-infected dog population is high. There is a strong correlation between frequency of Toxocara infection, life style, and infection risk. Institutionalization of mental retarded patients increases to risk of toxocariasis. In this study, we aimed at investigating the frequency of Toxocara infection among children with mental retardation not requiring institutionalization. The study included 96 cases, who had educatable mental retardation and 85 healthy subjects who comprised the control group. Anti-Toxocara IgG or IgM antibodies were investigated in all serum samples, using ELISA method. The frequency of Toxocara infection was found significantly higher in mental retarded cases than in those in the control group (18.8% and 7.1% respectively) (p < 0.05). There was no significant difference between mental retarded children and the control group in terms of mean age, age groups, gender, owning dogs and cats and duration of their ownership, socio-economic level and behavioural factors, and personal hygiene (p > 0.05). We did not find any significant difference between Toxocara seropositive and seronegative mental retarded children in terms of demographic factors and epidemiological factors that could increase the risk of Toxocara infection (p > 0.05). The present study is the first seroprevalence study carried out with a mental retarded group not requiring institutionalization. Determination of high frequency of Toxocara infection suggests that these subjects constitute a risk factor for Toxocara infection, which may be attributed to their behavioural patterns.
Memorias Do Instituto Oswaldo Cruz | 1999
Ahmet Kalkan; Vedat Bulut; Ozcan Erel; Senel Avci; Namik Kemal Bingol
In order to investigate purin and primidin metabolism pathways in hepatitis, adenosine deaminase (ADA) and guanosine deaminase (GDA) activities in sera of patients with different types and manifestations of viral hepatitis disease (A, B, C, D, E, chronic, acute) were investigated and compared with the control group of healthy individuals. Hepatitis cases were classified with respect to their serological findings and clinics. When compared all the hepatitis cases with the controls, levels of aspartate aminotransferase, alanine aminotransferase, and alkaline phosphatase enzymes, as well as ADA and GDA, were significantly higher than the control group (p<0.01). Levels of ADA and GDA in hepatitis cases were determined as 26.07 11.98 IU/l and 2.37 1.91 IU/l, respectively. When compared their ADA and GDA levels amongst the classified hepatitis groups, there was no difference in ADA levels amongst cases (p>0.05). However, GDA levels in hepatitis A group were closed to the controls. Increase in serum ADA activities in hepatitis forms may be dependent on and reflect the increase in phagocytic activity of macrophages and maturation of T-lymphocytes, and may be valuable in monitoring in viral hepatitis cases.