| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
|
|
|
|||||||
|
|||||||||
| ||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
Abstract
Various pathological stimuli such as radiation, environmental toxicants, oxidative stress and heat shock can initiate apoptosis in mammalian oocytes. Experiments were performed to examine whether apoptosis mediated by group II caspases is the cause for disruption of oocyte function by heat shock applied during maturation in cattle. Bovine cumulus-oocyte complexes (COCs) were cultured at 38.5, 40 or 41°C for the first 12 h of maturation. Incubation during the last 10 h of maturation, fertilization and embryonic development were at 38.5°C and 5% (v/v) CO2 for all treatments. In the first experiment, exposure of COCs to thermal stress during the first 12 h of maturation reduced cleavage rate and the number of oocytes developing to the blastocyst stage. In the second experiment, a higher percentage of TUNEL-positive oocytes was noted at the end of maturation for oocytes matured at 40 and 41°C than for those at 38.5°C. In addition, the distribution of oocytes classified as having high (>25 intensity units), medium (15-25 intensity units) and low (<15 intensity units) caspase activity was affected by treatment, with a greater proportion of heat-shocked oocytes having medium or high activity. In the third experiment, COCs were placed in maturation medium with vehicle [0.5% (v/v) DMSO] or 200 nM z-DEVD-fmk, an inhibitor of group II caspases. The COCs were matured at 38.5 or 41°C, fertilized and cultured for 8 days. The inhibitor blocked the effect of heat shock on cleavage rate and the percentage of oocytes and cleaved embryos developing to the blastocyst stage. In conclusion, heat shock during oocyte maturation can promote an apoptotic response mediated by group II caspases which, in turn, leads to disruption of the oocyte's capacity to support early embryonic development following fertilization.
Key words:
Environment •
Apoptosis •
Oocyte development
This article has been cited by other articles:
|
|
 |
|
  A. M Brad, K. E M Hendricks, and P. J Hansen The block to apoptosis in bovine two-cell embryos involves inhibition of caspase-9 activation and caspase-mediated DNA damage Reproduction, December 1, 2007; 134(6): 789 - 797. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 G. E. Schrock, A. M. Saxton, F. N. Schrick, and J. L. Edwards Early In Vitro Fertilization Improves Development of Bovine Ova Heat Stressed During In Vitro Maturation J Dairy Sci, September 1, 2007; 90(9): 4297 - 4303. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
B. Loureiro, A. M. Brad, and P. J. Hansen Heat shock and tumor necrosis factor-{alpha} induce apoptosis in bovine preimplantation embryos through a caspase-9-dependent mechanism Reproduction, June 1, 2007; 133(6): 1129 - 1137. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. M. Morton, W. P. Tranter, D. G. Mayer, and N. N. Jonsson Effects of Environmental Heat on Conception Rates in Lactating Dairy Cows: Critical Periods of Exposure J Dairy Sci, May 1, 2007; 90(5): 2271 - 2278. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
J. L. Edwards, A. M. Saxton, J. L. Lawrence, R. R. Payton, and J. R. Dunlap Exposure to a Physiologically Relevant Elevated Temperature Hastens In Vitro Maturation in Bovine Oocytes J Dairy Sci, December 1, 2005; 88(12): 4326 - 4333. [Abstract] [Full Text] [PDF]
|
|
|
|
 |
|
 M. Boelhauve, F. Sinowatz, E. Wolf, and F. F. Paula-Lopes Maturation of Bovine Oocytes in the Presence of Leptin Improves Development and Reduces Apoptosis of In Vitro-Produced Blastocysts Biol Reprod, October 1, 2005; 73(4): 737 - 744. [Abstract] [Full Text] [PDF]
|
|
|
|
|
|
Z Roth and P J Hansen Disruption of nuclear maturation and rearrangement of cytoskeletal elements in bovine oocytes exposed to heat shock during maturation Reproduction, February 1, 2005; 129(2): 235 - 244. [Abstract] [Full Text] [PDF]
|
|
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | ARCHIVE | SEARCH |
