The ultrastructure of Sorubim lima (Teleostei, Siluriformes, Pimelodidae) spermatogenesis: premeiotic and meiotic periods

The ultrastructure of Sorubim lima spermatogenesis during the premeiotic and meiotic periods was studied. Our observations showed that the germ cells in the cysts are connected by cytoplasmic bridges and the mitotic and meiotic divisions are slightly asynchronous, the first and the last spermatogonial generations differ in the cellular and nuclear volume, nucleolus, chromatin condensation, distribution, size, density, and shape of the mitochondria, presence of 'lamellae anulata', amount and dimension of the 'nuages', and movement of the centrioles. In addition to the nuclear prophase structures, the spermatocyte I shows changes in all other cellular organelles and elongated vesicles appear in the cytoplasm. The accentuated cytoplasmic density and thickened walled vesicles are morphological characteristics that differentiate spermatocytes II from the other germ cells in the cysts of Sorubim lima testis. (C) 1999 Harcourt Publishers Ltd.

Ultrastructure of Sorubim lima (Teleostei, Siluriformes, Pimelodidae) spermiogenesis

The spermiogenesis and the spermatozoon ultrastructure of Sorubim lima were studied. Our observations showed that early spermatids are round-shaped cells, have spherical nucleus with diffuse chromatin, small quantity of mitochondria and large amount of vesicles in the cytoplasm. During the differentiation process in the nucleus, chromatin compacts in a progressive and homogeneous way, and the flagellum is formed. In the cytoplasm the vesicles, that have double membranes, aggregate and fuse on the plasma membrane. The spermatozoa of 5. lima have no acrosome and show spherical nucleus with homogeneous and highly compacted chromatin, intermediary piece with mitochondria and double wall vesicles contiguous to the plasma membrane, as well as a flagellum formed by a basic axoneme (9 + 2).

Report of the Third Ministerial Conference on the Information Society in Latin America and the Caribbean: Lima, 21-23 November, 2010

Incluye bibliografía

Report of the thirty-fifth session. Lima, 5-9 May 2014

Attendance and organization of work .-- Agenda .-- Summary of proceedings .-- Resolutions adopted at the Thirty-Fifth Session of the Commission: 676(XXXV) ECLAC calendar of conferences for the period 2015-2016 .-- 677(XXXV) Regional Conference on Women in Latin America and the Caribbean .-- 678(XXXV) Statistical Conference of the Americas of the Economic Commission for Latin America and the Caribbean .-- 679(XXXV) Support for the work of the Latin American and Caribbean Institute for Economic and Social Planning .-- 680(XXXV) Caribbean Development and Cooperation Committee .-- 681(XXXV) Regional Conference on Population and Development in Latin America and the Caribbean .-- 682(XXXV) Establishment of the Regional Conference on Social Development in Latin America and the Caribbean .-- 683(XXXV) Admission of Sint Maarten as an associate member of the Economic Commission for Latin America and the Caribbean .-- 684(XXXV) Programme of Work and priorities of the Economic Commission for Latin America and the Caribbean for the 2016-2017 biennium .-- 685(XXXV) Activities of the Economic Commission for Latin America and the Caribbean in relation to follow-up to the Millennium Development Goals and implementation of the outcomes of the major United Nations conferences and summits in the economic, social and related fields .-- 686(XXXV) Application of Principle 10 of the Rio Declaration on Environment and Development in Latin America and the Caribbean .-- 687(XXXV) The regional dimension of the post-2015 development agenda .-- 688(XXXV) South-South Cooperation .-- 689(XXXV) Place of the next session .-- 690(XXXV) Lima Resolution .-- 691(XXXV) Ministerial Conference on the Information Society in Latin America and the Caribbean.