Ovarian follicle ultrastructure and changes in levles of ovarian steroids during oogenesis in Chalcalburnus tarichi Pallas, 1811

Chalcalburnus tarichfde kortikal alveolar, vitellogenez ve oosit olgunlaşması sırasında, ovaryum folikülünün ince yapısı ve ovaryumdaki 11-dehidrokortikosteron (11-DHC) östradiol-17ß $(E_2)$ , α-hidroksiprogesteron (17 $alpha$ -0HP), ve progesteron (P) seviyeleri incelendi. Kortikal alveolar safha sırasında, genç oosit yüzeyinde mikrovilluslar şekillenmeye başlar ve vitellogenez sırasında, granüloza hücrelerinden şekillenen mikrovilluslar ile zona radiata tabakasındaki kanallar vasıtasıyla bağlantı kurulur. Spesifik teka hücreleri tübüler kristali mitokondri, düz endoplazmik retikulum ve lipit damlaları gibi steroid salgılayan hücrelerin karakteristik yapılarını.içerirken, granüloza hücreleri protein salgılayan hücreler için tipik organelleri içerir (daha fazla granüllü endoplazmik retikulum ve gelişmiş Golgi kompleksi). Bu bulgular, C. tarichîüe, vitellogenez sırasında, spesifik teka hücrelerin steroid sentezleyen merkezler olduğunu göstermektedir.11-DHC ve P seviyeleri diğer hormonlardan daha düşük konsantrasyonlarda ölçüldü. 11-DHC seviyesi kortikal alveolar faz sırasında azalırken (52,60 ± 6,54'den 20,33 ±6,74 ng/ml'ye), vitellogenez sırasında dereceli olarak artarak vitellogenez sonunda en yüksek seviyeye ulaştı (68,90 ± 9,99 ng/ml). Olgunlaşma safhasının başında tekrar bazal seviyeye düştü (22,90 ± 1,87 ng/ml) ve olgunlaşma safhasının sonunda tekrar arttı (54 ± 0,75 ng/ml). E2 seviyesi kortikal alveolar fazda artmaya başladı ve bu artış vitellogenez boyunca da devam etti. Fakat Şubatta küçük bir düşüş görüldü. Bununla birlikte E2 seviyesi vitellogenez sonunda maksimum seviyeye ulaştı (756,10 ± 26,5 ng/ml), olgunlaşma fazında 213,50 ± 25,5 ng/ml'ye düştü ve Mayıs'ta tekrar bir artış görüldü. 17a-0HP seviyesi kortikal alveolar fazın başında 100,10 ± 14,4 ng/ml, fazın sonunda 13,40 ± 1,3 ng/ml'ye düştü. Onun seviyesi vitellogenez sırasında artmaya başladı ve safhanın sonunda maksimum değere ulaştı (213,90 ± 8,14 ng/ml). Olgunlaşma safhasının başında çok belirgin bir düşüş görüldü (68 ± 8,58 ng/ml) ve olgunlaşma sonunda (Mayıs) tekrar arttı. Progesteron seviyesi, kortikal alveolar fazın başında 50,90 ± 2,37 ng/ml ölçüldü ve fazın sonunda 22,80 ± 0,50 ng/ml'ye azaldı. Bu düşük değer vitellogenezin başında korundu fakat vitellogenez sırasında az bir artışla fazın sonunda 50,80 ± 4,03 ng/ml ölçüldü. Bu düşük seviye olgunlaşma fazında da korundu. Bu bulgular, C. tarichi'de 11-DHC, $E_2$, 17 $alpha$-OHP ve P'un kortikal alveolar faz sırasında etkili olmadığını, P'un vitellogenezde etkili olmazken E2, 11-DHC ve 17 $alpha$ -OHP'nin etkili olduğunu ve $E_2$ ve P'nin olgunlaşma sonunda (belki ovulasyonda) etkili olmazken 11-DHC ve 17 $alpha$ -0HP'nin etkili olduğunu gösterir.

İnci kefalinde (Chalcalburnus tarichi Pallas, 1811) oogenezis sürecinde ovaryum foliküllerinin ince yapısı ve ovaryumsteroid seviyelerinin değişimi

The ultrastructure of the ovarian follicle and the levels of the ovarian 11 -dehydrocorticosterone (11 -DHC), estradiol-17ß ($E_2$), 17 $alpha$ -hydroxyprogesterone (17 $alpha$ -0HP), and progesterone (P) were studied during cortical alveoli, vitellogenesis and oocyte maturation in Chalcalburnus tarichi. The microvilli began to form on the oocyte surface during cortical alveoli phase and during vitellogenesis, came into contact in the pore canals of the zona radiata with microvilli formed from granulosa cells. While the special thecal cells posses specific organelles, which are characteristic of steroid-producing cells, namely, mitochondria with tubular cristae, smooth endoplasmic reticulum and lipid droplets, the granulosa cells contain organelles typical for protein-secreting cells. These findings suggest that during vitellogenesis the special thecal cells are the sites of steroid synthesis in the C. tarichi ovary. The levels of 11-DHC and progesterone were measured at lower concentration than other hormones. While there was a decline in 11-DHC level during cortical alveoli phase (from 52.60 ± 6.54 to 20.33 ± 6.74 ng/ml), during vitellogenesis it increased gradually and reached a peak at the end of vitellogenesis (68.90 ± 9.99 ng/ml). At the beginning of maturation phase, it decreased to baseline level (22.90 ± 1.87 ng/ml) and again increased at the end of the maturation (54 ± 0.75 ng/ml). $E-2$ levels started to increase at cortical alveoli phase and this increase continued during vitellogenesis too. In February, a small decline was noted. However, at the end of vitellogenesis the level of $E_2$ reached its maximum value (756.10 ± 26.5 ng/ml). At the maturation phase (in April) it decreased to 213.50 ± 25.5 ng/ml and again a slight increase was perceived (in May). 17 $alpha$ -0HP level was 100.10 ± 14.4 ng/ml at the beginning of the cortical alveoli phase and it decreased to 13.40 + 1.3 ng/ml at the end of the phase. It started to increase during vitellogenesis and reached its maximum value at the end of vitellogenesis (213.90 ± 8.14 ng/ml). At the beginning of the maturation phase (in April) an evident decline was noted (68.00 + 8.58 ng/ml). It increased again to 142.20 ± 4.45 ng/ml at the end of maturation (in May). P level was measured to 50.90 ± 2.37 ng/ml at the beginning of the cortical alveoli phase (in August), and it decreased to 22.80 ± 0.50 ng/ml at the end of the phase. This low value was kept at the beginning of vitellogenesis, but during vitellogenesis a small increase was noted and at the end of the phase it was measured as 50.80 ± 4.03 ng/ml. This low level is kept during maturation phase too. These results suggest that in C. tarichi none of these hormones (11-DHC, $E_2$ , 17 $alpha$ - OHP and P) is effective during the cortical alveoli phase, $E_2$ , 11-DHC and 17 $alpha$ - OHP are effective during vitellogenesis while P has no effect and 11-DHC and 17 $alpha$ - OHP are effective at the end of maturation while $E_2$ and P have no role.

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