Two catalytic isoforms of the Na,K-ATPase, a1 and a4, are present in testis. While a1 is ubiquitously expressed in tissues, a4 predominates in male germ cells. Each isoform has distinct enzymatic properties and appears to play specific roles. To gain insight into the relevance of the Na,K-ATPase a isoforms in male germ cell biology, we have studied the expression and activity of a1 and a4 during spermatogenesis and epididymal maturation. This was explored in rat testes at different ages, in isolated spermatogenic cells and in spermatozoa from the caput and caudal regions of the epididymis. Our results show that a1 and a4 undergo differential regulation during development. Whereas a1 exhibits only modest changes, a4 increases with gamete differentiation. The most drastic changes for a4 take place in spermatocytes at the mRNA level, and with the transition of round spermatids into spermatozoa for expression and activity of the protein. No further changes are detected during transit of spermatozoa through the epididymis. In addition, the cellular distribution of a4 is modified with development, being diffusely expressed at the plasma membrane and intracellular compartments of immature cells, finally to localize to the midregion of the spermatozoon flagellum. In contrast, the a1 isoform is evenly present along the plasma membrane of the developing and mature gametes. In conclusion, the Na,K-ATPase a1 and a4 isoforms are functional in diploid, meiotic and haploid male germ cells, a4 being significantly upregulated during spermatogenesis. These results support the importance of a4 in male gamete differentiation and function.
Đối với các mỏ dầu có động thái chất lưu biến đổi phức tạp, để mô hình hóa chính xác đặc tính dầu khí theo điều kiện áp suất - thể tích - nhiệt độ (PVT) thường phải chia ra rất nhiều phân vùng, tiến hành thu thập và phân tích thêm nhiều mẫu chất lưu (trong thực tế, tại mỗi vùng thủy động lực phải có ít nhất một giếng khai thác được thu thập mẫu) mà kết quả vẫn chưa hoàn toàn chính xác. Ngoài ra, mức độ chi tiết còn bị giới hạn bởi số vùng chia hữu hạn trong khi xét về mặt không gian thì đặc tính PVT chất lưu của vỉa có sự biến đổi liên tục. Bài báo giới thiệu việc ứng dụng phương trình trạng thái trong điều kiện cân bằng nhiệt động học để đưa ra phương án mô hình hóa hiệu quả đặc tính chất lưu cho từng vị trí cụ thể trong không gian (biến đổi liên tục) vỉa Hamra thuộc vùng dầu khí Touggourt, sa mạc Sahara. Từ đó, có thể mô hình hóa đặc tính chất lưu biến đổi liên tục, giảm thiểu tối đa việc phải tiến hành thu thập và phân tích thêm mẫu chất lưu cũng như tiết giảm chi phí.
The finding of heavy oil at Dong Do field of Cuu Long basin is a success in exploration. It could be considered as a large heavy oil field offshore Vietnam. Maximising reserve is a challenge to the operator when they think of a suitable development strategy to efficiently and economically exploit the field. Over the past decades, production technology application in heavy oil production has been widely developed in the industry. Apart from the thermal method, pumping technology makes remarkable advances by enlarging the drawdown created over the conventional gas lift in several heavy oil projects. This paper presents all the production technology solutions that apply to the marginal heavy oil field offshore Vietnam. One of the major solutions is the electric submersible pump (ESP) and gas-lift (GL) combination method to enhance the wellbore lifting efficiency. In doing so, a series of solutions to improve heavy oil recovery have been conducted from design to pilot test whilst optimising the economic yield over the field life. Among them, the application of ESP and GL combination plays as the key driver to reinforce good production performance. As a result, the design includes an electrical pump system coupled with GL back-up, all integrated with one to boost production and prolong well life. Beside that, closely monitoring and optimising is one factor to give the pump a longer life.
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