Cryopreservation of Kunming mouse oocytes using slow cooling, ultrarapid cooling and vitrification protocols

The cryopreservation of oocytes has been only marginally successful with any of the current protocols, including slow cooling, rapid cooling and vitrification. We wished to test the hypothesis that oocytes from a single mouse strain would freeze successfully by 1 of the 3 mentioned protocols. Unfertilized Kunming mouse oocytes obtained 14 h after PMSG/hCG administration were randomly assigned to be cryopreserved after slow cooling, ultra rapid cooling and vitrification. Oocytes were thawed by straws being placed into 37 degrees C water, and their morphological appearance and in vitro fertilization capability were compared with that of oocytes that had not undergone cryopreservation. Survival of oocytes was indicated by the absence of darkened ooplasm or by broken membranes or zona pellucida. Functional integrity was evaluated by the formation of a 2-cell embryo after IVF. Survival rate of slow cooled oocytes did not differ from that seen in vitrified oocytes (55.1 vs 65.9%) but was significantly lower in the rapidly cooled oocytes (24.2%; P<0.01). The results of NF of slow cooled and vitrified oocytes were similar to those of the control group (72 and 73 vs 77%; P>0.05). It appears that Kunming mouse oocytes can be successfully cryopreserved using the slow cooling method with 1,2-propanediol and vitrification, which contains both permeating and nonpermeating cryoprotectants. (C) 1997 by Elsevier Science Inc.

Compensatory growth response in three-spined stickleback in relation to feed-deprivation protocols

Different protocols of food deprivation were used to bring two groups of juvenile three-spined sticklebacks Gaslerosteus aculeatus to the same reduced body mass in comparison with a control group fed daily ad libitum. One group experienced I week or deprivation then 2 weeks on maintenance rations. The second group experienced I week of ad lithium feeding followed by 2 weeks of deprivation. The deprived groups were reduced to a mean mass ore. 80% of controls. The compensatory growth response shown when ad libitum feeding was resumed was independent of the trajectory by which the three-spined sticklebacks had reached the reduced body mass. The compensatory response was Sufficient to return the deprived groups to the mass and length trajectories shown by the control group within 4 weeks. There was full compensation for dry mass and total lipid, but incomplete compensation for lipid-free dry mass. Hyperphagia and increased growth efficiency were present in the re-feeding phase, but there was a lag of a week before the hyperphagia was established. The consistency of the compensatory response of immature three-spined sticklebacks provides a potential model system for the analysis and prediction of appetite and growth in teleosts. (C) 2003 The Fisheries Society of the British isles.

Comparison of compensatory growth responses of juvenile three-spined stickleback and minnow following similar food deprivation protocols

The compensatory growth responses of individual juveniles of two co-existing species were compared after identical periods of starvation to determine inter-specific similarities and differences. The carnivorous stickleback Gasterosteus aculeatus was compared with the omnivorous minnow Phoxinus phoxinus. Both species experienced 1 or 2 weeks of starvation before being re-fed ad libitum. The two species differed in their response to the starvation periods, with minnows showing a lower weight-specific loss. Both species showed compensatory responses in appetite, growth and to a lesser extent, growth efficiency. Minnows wholly compensated for 1 and 2 weeks of starvation. At the end of the experiment, sticklebacks starved For 2 weeks were still showing a compensatory response and had nut achieved full compensation. The compensatory responses of the sticklebacks showed a lag of a week before developing in the re-feeding phase, whereas the response of the minnows was immediate. Analysis of lipid and dry matter concentrations suggested that the compensatory response restored reserve lipids while also bringing the fish back to the growth trajectory of continuously fed fish. (C) 2001 The Fisheries Society of the British Isles.