Person: TOKER, MEHMED BERK
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TOKER
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MEHMED BERK
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Publication Comparison and assessment of ovarian follicular dynamics during the breeding and non-breeding season in saanen goats(B W K Publishing Solutions & Verlag, 2020-01-01) Dogan, İbrahim; DOĞAN, İBRAHİM; Toker, Mehmed Berk; TOKER, MEHMED BERK; Alcay, Selim; ALÇAY, SELİM; Küçüksen, D. Udum; Veteriner Fakültesi; Biyokimya Bölümü; 0000-0003-1976-1814; A-2794-2014; R-8366-2018We describe and compare the ovarian follicular dynamics and plasma progesterone concentrations in nulliparous Saanen does during the breeding and non-breeding seasons. Does were monitored daily using transrectal ovarian ultrasonography for a full oestrous cycle in the breeding (n = 19) and a 21-day period in the non-breeding season (n = 20). At two-day intervals, blood samples were taken to determine plasma progesterone by ELISA. The pattern of follicular growth was characterised by four and five follicular waves in both seasons. Although the number of follicular waves was similar in the two seasons, the number of codominant follicles (p=0.027), the diameter of the largest follicle of waves 1 (p=0.036) and 4 (p=0.031), the duration of waves 3 (p=0.029) and 4 (p=0.034), the diameter of the largest follicle (p=0.042), the sums of the durations of all waves (p=0.037), the interwave interval (p=0.026) and the follicle growth rate (p=0.044) were higher in the breeding than in the non-breeding season. In addition, the numbers of small, medium and large follicles and the total number of all follicles of all waves differed between the seasons (p=0.037). In the breeding season, we found significant differences between the waves in the diameter of the largest follicles (p=0.042) and the duration of the waves (p=0.037); in the non-breeding season, no significant differences were found. Ovulatory follicles were most common in the fifth follicle wave. In the breeding season, the mean inter-oestrus and inter-ovulatory intervals and the numbers of ovulations after a synchronized oestrus with PGF2a were 21.47 +/- 0.19 days, 20.47 +/- 0.19 days and 1.84 +/- 0.86. The results indicate that follicular growth in Saanen goats during the breeding and non-breeding season is characterised by a wave-like pattern that differs between seasons.Publication Comprehensive effects of fetal calf serum in soybean-lecithin based goat semen cryopreservation extenders and impacts on incubation resilience(Kafkas Univ, Veteriner Fakultesi Dergisi, 2022-06-24) Toker, Mehmed Berk; TOKER, MEHMED BERK; Alcay, Selim; ALÇAY, SELİM; Veteriner Fakültesi; A-2794-2014The aim of this study was to investigate the effects of various fetal calf serum (FCS) doses on %1 soybean lecithin-based semen extenders for goat semen cryopreservation and the impacts on spermatological parameters over post-thaw and post-incubation (6 h) time periods. Sperm samples collected via electro-ejaculation method were pooled to overcome the individual differences and were used in the study. The samples then were split into four equal aliquots to create study groups as; 0.25%, 0.50%, 0.75% FCS supplemented and a sample of FCS-free control group. Each sample group was diluted to approximately 150 x 106 spermatozoon/mL final concentration and two step dilution method was used for cryopreservation. Study groups were examined for sperm motility, plasma membrane functional integrity with hypoosmotic swelling test (HOST), acrosome integrity by FITC-Pisum sativum agglutinin (PSA-FITC) and DNA damage by terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay (TUNEL). All samples were incubated for further 6 h in a humidified air chamber with 5% CO2 at 39 degrees C. The results indicated that FCS supplementation in soybean lecithin-based extenders for goat sperm cryopreservation had significant effects on post-thawing time point motility (P < 0.05), plasma membrane integrity (P < 0.05) and acrosomal integrity (P < 0.05) parameters. Subsequently to 6 h of incubation period, DNA integrity results yielded better scores comparing to control group in addition with other spermatological parameters (P < 0.05).Publication Drone semen cryopreservation with protein supplemented tl-hepes based extender(Kafkas Univ, Veteriner Fakultesi Dergisi, 2019-07-01) Alcay, Selim; ALÇAY, SELİM; Çakmak, Selvinar; Çakmak, İbrahim; ÇAKMAK, İBRAHİM; Mülkpınar, Emine; Toker, Mehmed Berk; TOKER, MEHMED BERK; Üstüner, Burcu; ÜSTÜNER, BURCU; Şen, Hasan; Nur, Zekariya; NUR, ZEKARİYA; Veteriner Fakültesi; 0000-0002-1438-221X; AAH-2635-2021; AAH-2558-2021; AAG-7238-2021; A-2794-2014The aim of the current study was to determine the optimum concentration of bovine serum albumin for post-thawing quality of drone sperm and this is the first study to evaluate the effect of BSA supplemented TL-Hepes based extenders for drone semen cryopreservation. Sexually mature drones were used for semen collection. Pooled semen was diluted with TL-Hepes based extender supplemented with different concentrations of BSA (1 mg/mL, 3 mg/mL, and 5 mg/mL) or without BSA (control), at a final concentration of 100x10(6) spermatozoon/mL. Motility, plasma membrane functional integrity (HOST), and defected acrosome (PSA-FITC) were evaluated in the study. At post thaw, the highest sperm motility rates were obtained in the BSA5 group (P< 0.05). Functional integrity of sperm membrane was better preserved in the BSA3 and BSA5 groups compared to the other groups. The acrosomal integrity rates were higher in BSA5 group than in control group (P< 0.05). The study shows that bovine serum albumin supplemented TL-Hepes based extenders have beneficial effect on drone semen parameters at post-thaw. The results of the study demonstrated a notable advantage of using 5 mg/mL of BSA in TL-Hepes based extender.Publication Does isoxsuprine hcl facilitate the passage of the cervix in sheep?: A case series(Sivar-soc Italiana Veterinari Animali Reddito, 2023-04-01) Önder, N. Tekin; Gökdemir, Taygun; Kılıç, Muhammet Can; Şahin, Oğuzhan; Yıldız, Savaş; Öztürkler, Yavuz; Toker, M. Berk; TOKER, MEHMED BERK; Veteriner Fakültesi; 0000-0003-4033-9749; A-2794-2014The complexity of the sheep cervix limits non-surgical artificial insemination and embryo production technologies. For this reason, assisted reproduction techniques are generally performed with surgical methods in sheep. But it is said that surgical methods can hurt the health and welfare of animals and cause them to feel stressed in different ways. Because of these problems with surgical methods and some difficulties in the application phase, researchers are trying to come up with ways to help with reproduction that don't involve surgery. For the application of non-surgical assisted reproductive techniques in sheep, there is a need for successful relaxation of the cervix. Because of this, different tocolytic agents have been used before non-surgical methods of assisted reproduction. Isoxsuprine HCl is used to relax the uterus during procedures like simple dystocia, to prevent premature birth, embryotomies, and caesarean deliveries. It is also used to treat horse navicular disease and laminitis in modern veterinary medicine. Tocolysis usually sets in about 10-15 minutes after an intramuscular isoxsuprine HCl administration. The aim of the present study was to evaluate the effects of isoxsuprine HCl on cervical dilatation in ewes. In our study, it has been thought that isoxsuprine HCl, which is also a tocolytic agent, might be an alternative for non-surgical reproductive uses. The study was carried out on a total of 20 animals: Ten sheep were given cervical relaxation with isoxsuprine HCl and ten animals were given no tocolytic agent. The mean cervical transition time was 83.60 +/- 13.63 seconds in animals treated with isoxsuprine HCl and 168.22 +/- 20.83 seconds in the control group. A significant difference was found between the groups (P<0.05). The minimum transition time was found to be 19 seconds in the isoxsuprine HCl group and 30 seconds in the control group. Maximum transition times were found at 140 and 238 seconds, respectively. As a result, it was seen that isoxsuprine HCl can offer a good alternative in transcervical applications in sheep.Publication Ovarian follicle dynamics and hormonal changes during early pregnancy in saanen goats(Czech Academy Agricultural Sciences, 2020-01-01) Doğan, İbrahim; Toker, Mehmed Berk; Alcay, Selim; Küçükşen, Duygu Udum; DOĞAN, İBRAHİM; TOKER, MEHMED BERK; ALÇAY, SELİM; UDUM, DUYGU; 0000-0003-1976-1814; 0000-0003-4033-9749; A-2794-2014; R-8366-2018; CBC-7350-2022; FGX-3813-2022This study is aimed at describing the ovarian follicular dynamics, corpora lutea and their hormonal control during early pregnancy in Saanen goats. The ovaries of pregnant goats (n = 10) were monitored daily for follicles (>= 2 mm) and corpora lutea by transrectal ultrasound over the 35 days after mating. Blood samples were collected by jugular venipuncture at the time of ultrasonography and were analysed for the concentrations of oestradiol (E-2) and progesterone (P-4), inhibin, FSH (follicle-stimulating hormone) and LH (luteinizing hormone). The pattern of follicular growth was characterised by five (n = 2; 20 %), six (n = 5; 50 %) and seven (n = 3; 30 %) follicular waves during early pregnancy. The first corpora lutea (size 6.8 +/- 0.4 mm, mean + SEM) were detected at 5.0 +/- 0.3 days after the mating with a maximum diameter (12.2 +/- 0.3 mm) observed on day 24.0 +/- 1.1 of pregnancy. The dominant follicle diameter of waves 1 and 4, and the duration of waves 1-4 and 7 were maximal during the early pregnancy period (P < 0.05). In addition, the inter-wave interval of the 5 waves was significantly (P < 0.05) longer compared to the six and seven inter-wave intervals (7.0 +/- 0.1, 5.8 +/- 0.1 and 5.0 +/- 0.2 days, respectively). Although the number of small and medium-sized follicles did not differ with the days post-breeding, the number of large-sized follicles in the same period significantly decreased between 16 and 26 days and was negatively correlated with the period of pregnancy (P < 0.05). The plasma LH and E-2 concentrations were negatively correlated with the P-4 concentration. The inhibin concentrations were negatively correlated with FSH, but positively correlated with the number of large-sized follicles. These results indicate that ovarian follicular growth during the first 35 days of pregnancy in goats was characterised by a wave-like pattern and there was a close relationship between the number of FSH peaks and the number of follicular waves.Publication Effect of hCG administration on ovulation and estrus in Saanen goats subjected to short-term estrus synchronization protocol during the breeding season(Hellenic Veterinary Medical Soc, 2023-04-01) Doğan, I.; Toker, M. Berk; Aktar, A.; Yılmaz, M. M.; Udum, D.; DOĞAN, İBRAHİM; TOKER, MEHMED BERK; Aktar, Ahmet; Yılmaz, Mehmet Melih; UDUM, DUYGU; Veteriner Fakültesi; Döllenme ve Suni Tohumlama Ana Bilim Dalı; 0000-0003-1976-1814; 0000-0002-2975-2594; 0000-0001-6050-791X; 0000-0001-7052-1694; A-2794-2014; R-8366-2018; GWC-2055-2022; AAH-5167-2021; CBC-1744-2022This study aimed to compare the effect of hCG administered at 24 or 36 h following a short-term estrus synchronization treatment on the ovulation time and estrus parameters in non-lactating Saanen goats during the breeding season. The estrus cycles of does were synchronized with an intravaginal sponge containing 60 mg of medroxyprogesterone acetate (MAP) for six days, and an injection of 125 & mu;g of d-cloprostenol at the time of sponge insertion in addition to an injection of 300 IU of eCG 24h before sponge removal.After removal of the sponges, does were injected intramuscularly either 1 ml physiological saline(0.9% NaCl) solution after 12 h (Group1/Control; n=10), 100 IU hCG after 24 h (Group2; n=9) or 100 IU hCG after 36 h (Group3; n=9). Estrus behavior after sponge removal was observed twice daily for 84 h using teaser bucks and transrectal ovarian ultrasonography was performed twice a day for seven days to determine small, medium and large follicle numbers, luteal development and the time of ovulation.Blood samples were collected on the same days to determine serum progesterone (P4) and estradiol (E2) concentrations. No significant differences were observed in terms of estrus parameters, ovarian structure and serum P4 and E2 concentrations between the hCG-treated groups and the control group.Average values observed for all groups: estrus response (53.57%), the interval from sponge removal to estrus and ovulation (35.2 h and 67.86 h, respectively), duration of estrus (18.4 h), the interval from estrus onset to ovulation (50.37 h), ovulation rate (96.43%), number of ovulations (1.36), ovulatory follicle diameter (6.86 mm), corpus luteum diameter (8.22 mm), follicle and luteal growth rate (1.17 and 0.68 mm/day, respectively). In conclusion, administration of hCG at 24 or 36 h following a short-term estrus synchronization protocol does not affect ovulation time, estrus parameters, and serum P4 and E2 concentrations in goats during the breeding season.Publication Methionine, cysteine, and butylated hydroxytoluene enhance cryosurvival of ram semen on post-thaw and post-incubation time points(Springer, 2023-06-01) Toker, Mehmed Berk; Doğan, İbrahim; TOKER, MEHMED BERK; DOĞAN, İBRAHİM; Veteriner Fakültesi; Üreme ve Suni Tohumlama Ana Bilim Dalı; 0000-0003-1976-1814; 0000-0003-4033-9749; A-2794-2014; R-8366-2018Despite there have been many experiments conducted about antioxidants, the best sole or combination use of antioxidants to include as a standard ingredient to freezing extenders is yet to be found. This study was designed to investigate the different doses of methionine (2.5 and 5 mM), cysteine (1 and 2 mM), and butylated hydroxytoluene (BHT) (1 and 2 mM) for ram semen cryopreservation on post-thaw and post-incubation (6 h) time points over spermatological parameters. Semen samples were collected from Kivircik rams via electro-ejaculator in breeding season. After essential spermatological evaluations, appropriate samples were pooled then split into 7 equal aliquots to create study groups (antioxidant free control, 2.5 mM methionine, 5 mM methionine, 1 mM cysteine, 2 mM cysteine, 1 mM BHT, and 2 mM BHT). Semen samples were put into French straws (0.25 mL), and freezing procedure (two-step) was conducted via a programmable gamete freezer. At both time points, motility, HOST, PSA-FITC, and TUNEL assays were made to discover the impacts of cryopreservation and incubation process over sperm cells. Antioxidant supplemented groups yielded better results compared to the control groups in terms of various spermatological parameters not only at post-thaw time point but after incubation for 6 h of time. The study demonstrated that supplementing sperm freezing extenders with previous antioxidants may create new approaches to cryopreservation procedures, and through increasing success rate of freezing, fertility results may increase to better results in near future.Publication The combined effect of melatonin implant and removal of buck seminal plasma on cryopreservation during the nonbreeding season(Mary Ann Liebert, Inc, 2022-09-20) Gökçe, Elif; Önder, N. Tekin; ÜSTÜNER, BURCU; ÜSTÜNER, HAKAN; Üstüner, Hakan; Yılmaz, M. Melih; Hüraydın, Oğuzhan; Toker, M. Berk; TOKER, MEHMED BERK; Veteriner Fakültesi; Üreme ve Suni Tohumlama Ana Bilim Dalı; 0000-0002-7678-3289; 0000-0001-6050-791X; A-2794-2014; GWC-2055-2022; AHB-0614-2022This study aimed to determine how melatonin (MT) and seminal plasma affected the freezability of buck sperm during the nonbreeding season. Semen was collected from eight bucks before (pre-MT) and after (post-MT) MT application in the nonbreeding season. Individual ejaculates were collected from the bucks, split into two equal groups according to the removal of seminal plasma (SP) (-) or nonremoval of SP (+). For washing, the groups of ejaculates were centrifuged, and the supernatant was separated, SP (-) and SP (+) ejaculates were diluted, then frozen. Semen samples were examined for sperm motility, plasma membrane integrity, defective acrosomes, DNA fragmentation, and mitochondrial membrane function at the native and post-thaw stages. When the general average post-thaw motility (p < 0.01), plasma membrane (p < 0.05), acrosome (p < 0.05), and DNA integrity rates (p < 0.05) and mitochondrial membrane potential (MMP) (p < 0.01) were evaluated, it was seen that MT administration caused a statistically significant improvement. The dramatic effect of nonremoval of seminal plasma on motility and plasma membrane integrity is more clearly observed in individual semen samples frozen in the pre-MT group (p < 0.05). Also, it was observed that removing seminal plasma in the post-MT group caused even milder post-thaw acrosome damage compared with the SP (+) group (p < 0.05). The effect of removing seminal plasma was not observed in terms of DNA integrity and MMP rates in pre- and post-MT groups. As a result, it was concluded that MT application and removal of seminal plasma in the nonbreeding season result in improvement in the freezability of buck semen.Publication Effect of gnrh treatment following a short-term estrous induction protocol on estrus and ovulation in saanen goats, during the transitional period(Hellenic Veterinary Medical Soc, 2020-10-01) Doğan, İbrahim; DOĞAN, İBRAHİM; Toker, Mehmed Berk; TOKER, MEHMED BERK; Alcay, Selim; ALÇAY, SELİM; Küçüksen, Duygu Udum; Veteriner Fakültesi; Biyokimya Ana Bilim Dalı; 0000-0003-1976-1814; R-8366-2018; A-2794-2014The objective of this study was to compare the effect on the ovulation time and estrus parameters of a GnRH agonist (buserelin acetate) administered 24 or 36 h following a short-term estrus induction and synchronization treatment in non-lactating Saanen goats during the transitional period. Goats received 20 mg FGA sponges for 6 days plus 300 IU eCG and 125 mu g d-cloprostenol 24 h prior to sponge removal. After removal of the sponges, goats were given either 1 ml physiological saline (0.9% NaCI) solution (Group 1; n = 9) after 12 h, 0.004 mg GnRH (Group 2; n = 10) after 24 h or 0.004 mg GnRH (Group 3; n = 10) after 36 h. The follicle development and ovulation in the ovaries were monitored by transrectal ultrasonography starting from the sponge application until the fifth day of the estrus cycle. Blood samples were collected on the same days to determine the plasma concentrations of progesterone (P-4) and estradiol (E-2). No statistical differences among groups were detected in any synchronization parameters, ultrasonic evaluations and plasma P-4 and E-2 concentrations. The evaluation of pooled data showed that the response of Saanen goats to treatments was comparable to the results of other published trials. Results of this study indicate that administration of GnRH at 24 h or 36 h after sponge removal, at the end of a short estrus induction and synchronization protocol, does not affect plasma P-4 and E-2 concentrations, estrus parameters and ovulation time in goats, during the transition period.Publication Effects of triton x-100 pretreatment of lyophilized and frozen-thawed ram sperm on preimplantation embryo developmental competence(Taylor & Francis Inc, 2022-02-19) Üstüner, Burcu; Yağcıoglu, Selin; Demir, Kamber; Gökce, Elif; Öztürk, Gül Bakirer; Birler, Sema; Pabuçcuoğlu, Serhat; Üstüner, Burcu; SAĞIRKAYA, HAKAN; ÜSTÜNER, BURCU; Sağırkaya, Hakan; Nur, Zekariya; NUR, ZEKARİYA; Alcay, Selim; ALÇAY, SELİM; Toker, Berk; TOKER, MEHMED BERK; Soylu, Mustafa Kemal; SOYLU, MUSTAFA KEMAL; Veteriner Fakültesi; Dölerme ve Suni Tohumlama Ana Bilim Dalı; 0000-0002-1438-221X; 0000-0003-4033-9749; 0000-0002-4690-1029; ACB-3704-2022In this study, it was aimed to determine the effect of destruction of lyophilized and frozen-thawed ram sperm plasma and acrosomal membrane on development of embryos produced by intracytoplasmic sperm injection (ICSI). Semen samples were divided into two groups for lyophilization (L) and freezing (F). For the removal of the plasma membrane, L and F groups were incubated with Triton X-100 (LTX-100 and FTX-100, respectively). Integrities of the plasma membrane, acrosome and chromatin structure were evaluated. Oocytes were injected with these sperm groups. Although no plasma membrane and acrosome integrities of the L (0.0%) group were detected, the plasma membrane integrity of the F group (69.4%) was significantly higher than the FTX-100 group (23.6%) (p < 0.05). The acrosome integrity of the FTX-100 group (3.80%) was significantly lower than the F group (55.6%) (p < 0.05). The chromatin integrities of L and F groups were higher than the Triton X-100 treated groups (p < 0.05). ICSIs with L, LTX-100, F and FTX-100 sperm were produced similar cleavage and blastocyst rates. In conclusion, data presented here confirm that ram spermatozoa can effectively be lyophilized and injected into oocytes for initiation of embryonic development and Triton X-100 pretreatment is not necessary while using lyophilized and frozen semen.