TY - JOUR
T1 - Pattern of vitellogenesis and follicle maturational competence during the ovarian follicular cycle of Fundulus heteroclitus
AU - Cerdá, Joan
AU - Calman, Bruce G.
AU - LaFleur, Gary J.
AU - Limesand, Sean
N1 - Funding Information:
This work was supported by a National Science Foundation grant (IBN-9306123) awarded to Dr. Robin A. Wallace and represents Con- tribution No. 15 of the Center for Advanced Studies in Marine Aquaculture at the Whitney Laboratory. Participation of J.C. was ®nanced by a postdoctoral fellowship from the Ministry of Education and Science (Spain). We thank Dr. Wallace for his continuous support and encouragement during the realization of this work. We also thank Dr. R. M. Greenberg for technical assistance with the Northern blot analysis, and Lynn Milstead and Jim Netherton for their help with the graphic material.
PY - 1996/7
Y1 - 1996/7
N2 - The patterns of vitellogenesis and follicle maturational competence were examined across the semilunar spawning cycle of Fundulus heteroclitus. Daily egg collection showed spawning cyclicity in six experimental groups, with a mean period between spawnings of 14.9 ± 0.3 days, indicated by the nonlinear regression sine-curve matching analysis. Each cycle was then dated from Day - 7 to Day 7, with Day 0 as the peak egg-collection day. Females from each group were sampled on selected days during two to three consecutive spawning cycles, and these days were each chronologically given a temporal relation to Day 0 to pool the data into a composite. The analysis of the size-frequency distribution of ovarian follicles ≤0.5-mm diameter across the composite revealed a constant recruitment of small follicles (0.5- to 0.7-mm diameter) into vitellogenesis, which was supported by the continuous presence of vitellogenin (Vtg) 1 mRNA in the liver of the females. The plasma levels of Vtg were also essentially constant across the cycle, except for a progressive decrease from Day -7 through Day 3 that could be related to a more active Vtg uptake by a dominant population of follicles up to 1.7 mm in diameter. A second and more selective recruitment of full-grown follicles (1.3- to 1.4- mm diameter) toward maturation was noted at Days -5, -4, which appeared associated with high plasma levels of estradiol-17β. However, the responsiveness of those follicles undergoing oocyte maturation in vitro after gonadotropin and maturation-inducing steroid (MIS), 17,20β-dihydroxy-4- pregnen-3-one, stimulation dramatically declined from Days -1, 0, 1 to Days 4, 5, concomitantly with an increase of the population of the largest follicles (1.8- to 2.1-mm diameter) in the ovary. These findings extend previous observations on the process of follicular recruitment in F. heteroclitus and indicate that full-grown follicles may be recruited into maturation by a mechanism that modulates the oocyte sensitivity to the MIS.
AB - The patterns of vitellogenesis and follicle maturational competence were examined across the semilunar spawning cycle of Fundulus heteroclitus. Daily egg collection showed spawning cyclicity in six experimental groups, with a mean period between spawnings of 14.9 ± 0.3 days, indicated by the nonlinear regression sine-curve matching analysis. Each cycle was then dated from Day - 7 to Day 7, with Day 0 as the peak egg-collection day. Females from each group were sampled on selected days during two to three consecutive spawning cycles, and these days were each chronologically given a temporal relation to Day 0 to pool the data into a composite. The analysis of the size-frequency distribution of ovarian follicles ≤0.5-mm diameter across the composite revealed a constant recruitment of small follicles (0.5- to 0.7-mm diameter) into vitellogenesis, which was supported by the continuous presence of vitellogenin (Vtg) 1 mRNA in the liver of the females. The plasma levels of Vtg were also essentially constant across the cycle, except for a progressive decrease from Day -7 through Day 3 that could be related to a more active Vtg uptake by a dominant population of follicles up to 1.7 mm in diameter. A second and more selective recruitment of full-grown follicles (1.3- to 1.4- mm diameter) toward maturation was noted at Days -5, -4, which appeared associated with high plasma levels of estradiol-17β. However, the responsiveness of those follicles undergoing oocyte maturation in vitro after gonadotropin and maturation-inducing steroid (MIS), 17,20β-dihydroxy-4- pregnen-3-one, stimulation dramatically declined from Days -1, 0, 1 to Days 4, 5, concomitantly with an increase of the population of the largest follicles (1.8- to 2.1-mm diameter) in the ovary. These findings extend previous observations on the process of follicular recruitment in F. heteroclitus and indicate that full-grown follicles may be recruited into maturation by a mechanism that modulates the oocyte sensitivity to the MIS.
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U2 - 10.1006/gcen.1996.0090
DO - 10.1006/gcen.1996.0090
M3 - Article
C2 - 8812325
AN - SCOPUS:0030199882
SN - 0016-6480
VL - 103
SP - 24
EP - 35
JO - General and comparative endocrinology
JF - General and comparative endocrinology
IS - 1
ER -