Transient changes in intracellular calcium ([Ca2+]i) have been shown to punctuate the cell cycle in various types of cells in culture and in early embryos. The [Ca2+]i transients are correlated with cell-cycle events: pronuclear migration, nuclear envelope breakdown, the metaphase-anaphase transition of mitosis, and cytokinesis. Mitotic events can be induced by injecting calcium and prevented by injecting calcium chelators into the sea urchin embryo. Cell-cycle calcium transients differ from the transients linked to membrane signal transduction pathways: they are generated by an endogenous mechanism, not by plasma membrane receptor complexes, and their trigger is unknown. We report here that the phosphoinositide messenger system oscillates during the early embryonic cell cycle in the sea urchin, leading to cyclic increases in inositol trisphosphate that trigger cell-cycle [Ca2+]i transients and mitosis by calcium release from intracellular stores.

Abstract. Using calcium-sensitive dyes together with their dextran conjugates and confocal microscopy, we have looked for evidence of localized calcium signaling in the region of the nucleus before entry into mitosis, using the sea urchin egg first mitotic cell cycle as a model. Global calcium transients that appear to originate from the nuclear area are often observed just before nuclear envelope breakdown (NEB). In the absence of global increases in calcium, confocal microscopy using Calcium Green-1 dextran indicator dye revealed localized calcium transients in the perinuclear region.We have also used a photoinactivatable calcium chelator, nitrophenyl EGTA (NP-EGTA), to test whether the chelator-induced block of mitosis entry can be reversed after inactivation of the chelator. Cells arrested before NEB by injection of NP-EGTA resume the cell cycle after flash photolysis of the chelator. Photolysis of chelator triggers calcium release. Treatment with caffeine to enhance calcium-induced calcium release increases the amplitude of NEB-associated calcium transients. These results indicate that calcium increases local to the nucleus are required to trigger entry into mitosis. Local calcium transients arise in the perinuclear region and can spread from this region into the cytoplasm. Thus, cell cycle calcium signals are generated by the perinuclear mitotic machinery in early sea urchin embryos. INTRACELLULAR calcium is now known to perform a wide variety of functions as a second messenger. It is implicated in the control of exocytosis, protein synthesis, locomotion, and synaptic transmission (for reviews see Campbell, 1983;Berridge, 1993; Brostrom and Brostrom, 1990;Rasmussen and Rasmussen, 1990). It is increasingly clear that calcium signals can originate in specific cytoplasmic domains (Lechleiter et al., 1991;Rizzuto et al., 1993;Meyer et al., 1995;Petersen, 1995;Kasai, 1995). A body of evidence also points to a role for calcium ions as one of the mechanisms enabling passage through cell cycle control points (for reviews see Whitaker and Patel, 1990;Steinhardt, 1990;Lu and Means, 1993;Whitaker, 1995).The evidence for a role of calcium ions during mitosis comes from observations that embrace many different aspects of cell cycle physiology. For example, many components of the intracellular calcium signaling system localize to the area of the nucleus just before mitosis entry and to the mitotic apparatus during mitosis (Silver et al., 1980; Keihart, 1981;Petzelt, 1979Petzelt, , 1984Petzelt and Hafner, 1986;Wolniak et al., 1981; Paweletz and Firze, 1981;Hepler, 1980; Wolniak, 1983, 1984 as EGTA and BAPTA blocks both entry into, and exit from, mitosis (Steinhardt and Alderton, 1988;Twigg et al., 1988;Whitaker and Patel, 1990;Patel et al., 1989Patel et al., , 1990Ohsumi and Anraku, 1983;Iida et al., 1990; Lindsay et al., 1995). Entry into mitosis can also be induced prematurely by microinjection of calcium during a defined period before mitosis entry (Steinhardt and Alderton, 1988;Twigg et al., 1988;Patel et al., 1989...

Surgical treatments such as the Roux-en-Y gastric bypass operation result in the successful treatment of morbid obesity; however, this type of operation may cause long-term side effects due to the reduced absorption of nutrients. Here, we present data suggesting that this operation can result in secondary infertility in males. Six healthy, previously fertile male subjects presented in our centre for secondary infertility after a Roux-en-Y gastric bypass operation for morbid obesity. Reproductive function was assessed with a series of spermiograms, and by testicular biopsy. Secondary azoospermy with complete spermatogenic arrest was diagnosed. The results suggest that weight reduction surgery may cause reproductive dysfunction.

These data suggest that calmodulin regulates mitotic transitions and demonstrate the utility of fluorescent adducts for studying protein activation in living cells with good temporal and spatial resolution.

These results suggest that patients with initial inadequate responses to rFSH after pituitary downregulation benefit from the addition of a daily dose of 150 IU of rLH, starting from the eighth day of stimulation.