Fatma Uysal

2100-MHz electromagnetic fields have different effects on visual evoked potentials and oxidant/antioxidant status depending on exposure duration.

The purpose of the present study was to investigate the duration effects of 2100-MHz electromagnetic field (EMF) on visual evoked potentials (VEPs) and to assess lipid peroxidation (LPO), nitric oxide (NO) production and antioxidant status of EMF exposed rats. Rats were randomized to following groups: Sham rats (S1 and S10) and rats exposed to 2100-MHz EMF (E1 and E10) for 2h/day for 1 or 10 weeks, respectively. At the end of experimental periods, VEPs were recorded under anesthesia. Brain thiobarbituric acid reactive substances (TBARS) and 4-hydroxy-2-nonenal (4-HNE) levels were significantly decreased in the E1 whereas increased in the E10 compared with their control groups. While brain catalase (CAT), glutathione peroxidase (GSH-Px) activities and NO and glutathione (GSH) levels were significantly increased in the E1, reduction of superoxide dismutase (SOD) activity was detected in the same group compared with the S1. Conversely, decreased CAT, GSH-Px activities and NO levels were observed in the E10 compared with the S10. Latencies of all VEP components were shortened in the E1 compared with the S1, whereas latencies of all VEP components, except P1, were prolonged in the E10 compared with the S10. There was a positive correlation between all VEP latencies and brain TBARS and 4-HNE values. Consequently, it could be concluded that different effects of EMFs on VEPs depend on exposure duration. In addition, our results indicated that short-term EMF could provide protective effects, while long-term EMF could have an adverse effect on VEPs and oxidant/antioxidant status.

DNA methyltransferases exhibit dynamic expression during spermatogenesis

DNA methylation is one of the epigenetic marks and plays critically important functions during spermatogenesis in mammals. DNA methylation is catalysed by DNA methyltransferase (DNMT) enzymes, which are responsible for the addition of a methyl group to the fifth carbon atom of the cytosine residues within cytosine-phosphate-guanine (CpG) and non-CpG dinucleotide sites. Structurally and functionally five different DNMT enzymes have been identified in mammals, including DNMT1, DNMT2, DNMT3A, DNMT3B and DNMT3L. These enzymes mainly play roles in two DNA methylation processes: maintenance and de novo. While DNMT1 is primarily responsible for maintenance methylation via transferring methyl groups to the hemi-methylated DNA strands following DNA replication, both DNMT3A and DNMT3B are capable of methylating unmodified cytosine residues, known as de novo methylation. However, DNMT3L indirectly participates in de novo methylation, and DNMT2 carries out methylation of the cytosine 38 in the anticodon loop of aspartic acid transfer RNA. To date, many studies have been performed to determine spatial and temporal expression levels and functional features of the DNMT in the male germ cells. This review article comprehensively discusses dynamic expression of the DNMT during spermatogenesis and their relationship with male infertility development in the light of existing investigations.

DNMT1, DNMT3A and DNMT3B proteins are differently expressed in mouse oocytes and early embryos

DNA methylation is one of the epigenetic mechanisms and plays important roles during oogenesis and early embryo development in mammals. DNA methylation is basically known as adding a methyl group to the fifth carbon atom of cytosine residues within cytosine–phosphate–guanine (CpG) and non-CpG dinucleotide sites. This mechanism is composed of two main processes: de novo methylation and maintenance methylation, both of which are catalyzed by specific DNA methyltransferase (DNMT) enzymes. To date, six different DNMTs have been characterized in mammals defined as DNMT1, DNMT2, DNMT3A, DNMT3B, DNMT3C, and DNMT3L. While DNMT1 primarily functions in maintenance methylation, both DNMT3A and DNMT3B are essentially responsible for de novo methylation. As is known, either maintenance or de novo methylation processes appears during oocyte and early embryo development terms. The aim of the present study is to investigate spatial and temporal expression levels and subcellular localizations of the DNMT1, DNMT3A, and DNMT3B proteins in the mouse germinal vesicle (GV) and metaphase II (MII) oocytes, and early embryos from 1-cell to blastocyst stages. We found that there are remarkable differences in the expressional levels and subcellular localizations of the DNMT1, DNMT3A and DNMT3B proteins in the GV and MII oocytes, and 1-cell, 2-cell, 4-cell, 8-cell, morula, and blastocyst stage embryos. The fluctuations in the expression of DNMT proteins in the analyzed oocytes and early embryos are largely compatible with DNA methylation changes and genomic imprintestablishment appearing during oogenesis and early embryo development. To understand precisemolecular biological meaning of differently expressing DNMTs in the early developmental periods, further studies are required.

The poly(A)-binding protein genes, EPAB, PABPC1, and PABPC3 are differentially expressed in infertile men with non-obstructive azoospermia

PurposeAzoospermia is one of the major causes of male infertility and is basically classified into obstructive (OA) and non-obstructive azoospermia (NOA). The molecular background of NOA still largely remains elusive. It has been shown that the poly(A)-binding proteins (PABPs) essentially play critical roles in stabilization and translational control of the mRNAs during spermatogenesis.MethodsIn the present study, we aim to evaluate expression levels of the PABP genes, EPAB, PABPC1, and PABPC3, in the testicular biopsy samples and in the isolated spermatocyte (SC) and round spermatid (RS) fractions obtained from men with various types of NOA including hypospermatogenesis (hyposperm), RS arrest, SC arrest, and Sertoli cell-only syndrome (SCO).ResultsIn the testicular biopsy samples, both PABPC1 and PABPC3 mRNA expressions were gradually decreased from hyposperm to SCO groups (P < 0.05), whereas there was no remarkable difference for the EPAB expression among groups. The expression levels of cytoplasmically localized PABPC1 and PABPC3 proteins dramatically reduced from hyposperm to SCO groups (P < 0.05). In the isolated SC and RS fractions, the EPAB, PABPC1, and PABPC3 mRNA expressions were gradually decreased from hyposperm to SC arrest groups (P < 0.05). Similarly, both PABPC1 and PABPC3 proteins were expressed at higher levels in the SC and RS fractions from hyposperm group when compared to the SC and RS fractions from either RS arrest or SC arrest group (P < 0.05).ConclusionOur findings suggest that observed significant alterations in the PABPs expression may have an implication for development of different NOA forms.

Potential roles of the poly(A)-binding proteins in translational regulation during spermatogenesis

Spermatogenesis is briefly defined as the production of mature spermatozoa from spermatogonial stem cells at the end of a strictly regulated process. It is well known that, to a large extent, transcriptional activity ceases at mid-spermiogenesis. Several mRNAs transcribed during early stages of spermatogenesis are stored as ribonucleoproteins (RNPs). During the later stages, translational control of these mRNAs is mainly carried out in a time dependent-manner by poly(A)-binding proteins (PABPs) in cooperation with other RNA-binding proteins and translation-related factors. Conserved PABPs specifically bind to poly(A) tails at the 3′ ends of mRNAs to regulate their translational activity in spermatogenic cells. Studies in this field have revealed that PABPs, particularly poly(A)-binding protein cytoplasmic 1 (Pabpc1), Pabpc2, and the embryonic poly(A)-binding protein (Epab), play roles in the translational regulation of mRNAs required at later stages of spermatogenesis. In this review article, we evaluated the spatial and temporal expression patterns and potential functions of these PABPs in spermatogenic cells during spermatogenesis. The probable relationship between alterations in PABP expression and the development of male infertility is also reviewed.

Peripheral apelin mediates stress‐induced alterations in gastrointestinal motor functions depending on the nutritional status

Exposure to stress induces gastrointestinal (GI) dysmotility. In rodents, acute restraint stress (ARS) inhibits gastric emptying (GE) and intestinal transit (IT) via central and peripheral corticotropin‐releasing factor (CRF)‐mediated pathways. Peripherally administered apelin‐13 was shown to inhibit GI motor functions; moreover, stress‐induced upregulation of gastric apelin content was demonstrated in rats suggesting that peripheral apelin may mediate stress‐induced alterations in GI motility. We investigated the role of endogenous peripheral apelin in stress‐induced GI dysfunction. GE, IT and gastro‐duodenal fasting motility were measured in non‐stressed (NS), CRF‐injected and ARS‐loaded rats. CRF and apelin receptor antagonists astressin or F13A was administered before ARS or peripheral CRF injection. Apelin and APJ receptor expressions were determined using immunohistochemistry and quantified by qRT‐PCR. Double immunofluorescence was performed for enteric neuronal apelin. GE and IT were delayed by CRF and ARS. ARS‐induced changes were attenuated by F13A, whereas astressin was ineffective. CRF‐induced alterations in GE and IT were restored completely by astressin, while they were diminished by F13A. Antral phase III‐like contractions were disturbed following ARS which were preserved by preadministration of astressin, but not F13A. CRF impaired gastric and duodenal fasting contractions, while these changes were not altered by F13A. ARS increased apelin expression in stomach and duodenum. Apelin immunoreactivity was detected in mucosa, smooth muscles and myenteric plexi, whereas dense APJ receptor expression was observed within tunica muscularis. APJ receptor was downregulated in rats fasted overnight. These results suggest that enteric apelin acts as an inhibitor stress mediator in the postprandial state.

Poly(A)-binding proteins are required for translational regulation in vertebrate oocytes and early embryos

Poly(A)-binding proteins (PABPs) function in the timely regulation of gene expression during oocyte maturation, fertilisation and early embryo development in vertebrates. To this end, PABPs bind to poly(A) tails or specific sequences of maternally stored mRNAs to protect them from degradation and to promote their translational activities. To date, two structurally different PABP groups have been identified: (1) cytoplasmic PABPs, including poly(A)-binding protein, cytoplasmic 1 (PABPC1), embryonic poly(A)-binding protein (EPAB), induced PABP and poly(A)-binding protein, cytoplasmic 3; and (2) nuclear PABPs, namely embryonic poly(A)-binding protein 2 and nuclear poly(A)-binding protein 1. Many studies have been undertaken to characterise the spatial and temporal expression patterns and subcellular localisations of PABPC1 and EPAB in vertebrate oocytes and early embryos. In the present review, we comprehensively evaluate and discuss the expression patterns and particular functions of the EPAB and PABPC1 genes, especially in mouse and human oocytes and early embryos.

DNA Methyltransferases in Mammalian Oocytes

Epigenetic mechanisms play important roles in properly occurring mammalian oogenesis. One of these mechanisms is DNA methylation adding a methyl group to the fifth carbon atom of the cytosine residues using S-adenosyl-L-methionine as a methyl donor. DNA methylation generally takes place at cytosine-phosphate-guanine (CpG) dinucleotide sites and rarely occurs at cytosine-phosphate-thymine (CpT), cytosine-phosphate-adenine (CpA), or cytosine-phosphate-cytosine sites, known as non-CpG sites. Basically, two different DNA methylation processes are identified: de novo methylation and maintenance methylation. While the de novo methylation functions in methylation of unmethylated DNA strands, maintenance methylation is capable of methylating hemi-methylated DNA strands following DNA replication. Both DNA methylation processes are catalyzed by special DNA methyltransferase (DNMT) enzymes. To date, five different DNMTs have been identified: DNMT1, DNMT3A, DNMT3B, DNMT3L, and DNMT2. In this chapter, we focus particularly on temporal and spatial expression of DNMTs in mammalian oocytes and granulosa cells.

Bilateral total ovarian hypoplasia in a Holstein Friesian heifer.

A report of a female Holstein Friesian heifer with ovarian hypoplasia is presented. The heifer had normal female external genitalia, but showed neither estrus nor became pregnant after siring with a fertile bull. At necropsy the vagina, uterine body and uterine horns appeared normal. Bilateral streak structures surrounded by mesovarium were observed and dissected for further investigation. Histological investigation revealed that a case of bilateral total ovarian hypoplasia was the cause of infertility. This is the first published report of ovarian hypoplasia from Antalya province in Turkey.