Current status of germline stem cells in adult mammalian ovary

The evolutionary and biological mechanisms underlying female reproductive aging have long been a matter of interest. Reproductive biologists have tackled with the relatively limited fertile period in female lifespan compared to male fertility that continues until the late ages. For more than five decades, it has been believed that females are born with a fixed number of germ cells that constitute ovarian follicle reserve and depletion of this reserve causes menopause. However, researchers recently reported findings that support the presence of oogenesis in postnatal mammalian ovaries, which caused a paradigm shift in our current knowledge of reproductive biology. In this minireview, we provide a brief history of one of the central dogmas in reproductive biology and subsequently present recent studies on the existence of germline stem cells in the mammalian ovary.Dişi üreme sistemi yaşlanmasının altında yatan evrimsel ve biyolojik mekanizmalar uzun süredir ilgi çeken bir konu olmuştur. Üreme biyolojisi konusunda çalışan biyologlar, erkeklerde ileri yaşlara kadar devam eden fertilite ile karşılaştırıldığında dişi yaşamında görece olarak sınırlı bir dönemde görülen fertilite konusunu aydınlığa kavuşturmaya çalışmaktadırlar. 50 yılı aşkın bir süredir dişilerin ovaryan folikül rezervini oluşturan sabit sayıda germ hücresi ile dünyaya geldiklerine inanılmaktadır. Ancak, son dönemde araştırıcılar memeli ovaryumlarında doğum sonrası oogenez varlığını destekleyen ve üreme biyolojisi ile ilgili günümüz bilgilerimizde değişime yol açan bulgular elde etmişlerdir. Bu derleme çalışmasında, üreme biyolojisindeki santral dogmalardan bir tanesi ile ilgili kısa bir tarihsel bilgi verilmiş ve memeli ovaryumlarında germ hattı kök hücrelerinin varlığı ile ilgili son dönem çalışmaları sunulmuştur

The effect of maternal vitamin D levels on placental shear wave elastography findings in the first trimester

The aim of this study was to investigate the effect of maternal serum Vitamin D levels on the elasticity of placenta. Seventy-four spontaneously conceived singleton pregnancies in their first trimester were enrolled into this study. Fifty-one of them had Vitamin D deficiency ( .05). Placental elasticity was not found to be different in the pregnancies with Vitamin D deficiency during the first trimester.IMPACT STATEMENT What is already known on this subject? The pSWE technique provides opportunity to determine the elasticity of any interested tissue. Placental elasticity has been found to be changed in inflammatory and fibrotic conditions such as in preeclampsia, intrauterine growth restriction or diabetes. On the other hand, Vitamin D deficiency is linked with several comorbidities such as autoimmune disorders, cancer and cardiovascular disorders. Vitamin D also plays a role in placental angiogenesis in the first trimester. Maternal Vitamin D levels are shown to be related with adverse pregnancy outcomes. What do the results of this study add? To the best of our knowledge, this study is the first assessing the association between Vitamin D levels and placental elasticity. Placental elasticity was not found to be changed by Vitamin D deficiency. What are the implications of these findings for clinical practice and/or further research? Our pilot study revealed that Vitamin D deficiency does not have any impact on placental elasticity in the first trimester. However, longitudinal studies concerning placental elasticity in subsequent trimesters are needed to support our findings