MITOCHONDRIOGENESIS IN MATURING SEA URCHIN OOCYTES: A COMPUTERIZED RECONSTRUCTION ANALYSIS

Abstract The dynamics of chondriome changes in oogenesis of the sea urchinParacentrotus lividuswere studied by electron microscopy. An oocyte-enriched fraction obtained by gonad mechanical dissociation without protease treatment was used. The shape, size and arrangement of mitochondria (Mt) in cells were quantitatively analysed on the basis of data from reconstruction experiments, with serial sections performed using a specific computer program. At all stages of oogenesis, the chondriome was shown to consist of rod-shaped Mt of various lengths and also of small amounts of globular Mt about 0.3 μm in diameter. Chondriome transformation during oogenesis is shown to involve the following proce…

MITOCHONDRIAL MASS, DISTRIBUTION AND ACTIVITY DURING SEA URCHIN OOGENESIS

The sea urchin egg is a favourite model for studies of the molecular biology and physiology of fertilization and early development, yet we know sparingly little of its oocytes and of mitochondria behaviour during oogenesis. The process of oogenesis in most echinoderms is asynchronous so each ovary lobe has hundreds of oocytes at all stages of development. At the beginning of oogenesis, the oocyte is about 10 µm in diameter. During the vitellogenic phase of oogenesis, the oocyte accumulate yolk proteins and grow to ten times their original size to 80 to 100 µm in sea urchins. The oocyte, arrested at the prophase of the first meiotic division, is apparent with its large nucleus, the germinal …

Supramaximal exercise mobilizes hematopoietic progenitors.

Plasma leptin or VEGF are little affected by maximal exercise at high altitude (5050 m)

Water recycling in leaves of Lithops (Aizoaceae)

Lithops plants consist of a pair of succulent leaves inserted on a short stem; in each growing season, young leaves develop in a cavity formed between the older pair. Young leaves can take up water from the older pair allowing the plant to maintain growth and leaf expansion even without external supply of water. Recycling water between vegetative organs is one of the possible adaptation strategies of plants under drought stress, but it had never been demonstrated experimentally in Lithops. The methodology used to verify the existence of water redistribution from old leaves to young leaves was fluorescence microscopy, using two dyes to follow the water pathway inside the plant: Sulforhodamin…