Insulin-Like Growth Factor-2 Regulation of Conceptus Composition: RESULTS(2)

RESULTS(2)

Recombination Experiments

The development of the recombined blastocysts to viable E16.5 conceptuses was recorded (Table 2). There was no evidence that an Igf2 ko component in either the trophec-toderm or the ICM derivatives influenced the success of development after the operation and transplantation. buy birth control online

Further analysis was restricted to the 13 litters with 46 viable conceptuses in one horn of the uterus, with a mean of 5.15 viable conceptuses per horn (see Materials and Methods). The combinations of genotypes produced by microsurgery were ICM Igf2 ko + normal trophectoderm, normal ICM + trophectoderm Igf2 ko, and normal ICM + normal trophectoderm.

Volume of Fluid in the Exocelomic and Amniotic Cavities

When either the trophectoderm or the ICM was Igf2 ko. then the volume bounded by the yolk sac at E16.5 was reduced (Table 3). The fluid volumes in the exocelomic and amniotic cavities were estimated, and they were significantly reduced when the yolk sac and fetus were Igf2 ko (ICM series, Table 3). Thus IGF-2 deficiency in the whole con-ceptus (Table 1) or in ICM derivatives reduced fluid transport from the mother or fluid retention by the conceptus.

Wet Weight of Placenta, Yolk Sac, and Fetus

When the E16.5 conceptuses were derived from blastocysts that were Igf2 ko in either the trophectoderm or the ICM, then the wet weights of all three parts were significantly reduced (Table 4). With the ICM Igf2 ko, the weight losses were greatest in the yolk sacs and fetuses (26-27%). With the trophectoderm Igf2 ko, the weight losses were greatest in the placentas (21%). The severest effects of IGF-2 deficiency on wet weight were therefore localized to the regions that lacked active Igf2 genes. Note that in these recombination experiments, the fetal placenta fraction did not contain all the derivatives of the trophectoderm: the giant cells and much of the spongiotrophoblast were removed to clear most maternal components.

DNA Contents of Placenta, Yolk Sac, and Fetus

In general, the DNA contents of the three parts of the conceptus showed a pattern of reduction similar to that of wet weights (Table 5). However, in no case were the reductions significant.

TABLE 3. Volumes of extraembryonic cavities in recombined conceptuses comparing conceptuses with one part Igf2 ko with all the normals in the same litters (mean ± SD).

Series n Fluid volume bounded by visceral yolk sac (ml) Fluid volume of exocoelomic and amniotic cavities (ml)
ICM Igf2 ko
Normal 15 0.939 ± 0.152 0.296 ± 0.125
Igf2 ko 17 0.606 ± 0.059a 0.135 ± 0.025b
Percent normal (Cl) 65% (55-74%) 58% (22-70%)
Trophectoberm Igf2 ko
Normal 8 0.890 ± 0.102 0.172 ± 0.051
Igf2 ko 11 0.757 ± 0.174c 0.184 ± 0.097d
Percent normal (Cl) 85% (71-99%) 107% NS

ap < 0.0001; bp < 0.0002; cp < 0.04; d p < 0.72.

TABLE 4. Wet weight of various genotype combinations comparing conceptuses with one part Igf2 ko with all the normals in the same litters (mean ± SD).*

Weight (g)
Series n Fetal placenta Yolk sac Fetus
ICM
Normal 16 0.056 ± 0.008 0.038 ± 0.006 0.607 ± 0.137
Igf2 ko 18 0.048 ± 0.012a 0.028 ± 0.006b 0.445 ± 0.050c
Percent normal (CI) 86% (74-99%) 74% (61-83%) 73% (61-86%)
Trophectoderm
Normal 9 0.053 ± 0.005 0.043 ± 0.006 0.672 ± 0.073
Igf2 ko 15 0.042 ± 0.005e 0.038 ± 0.005d 0.059 ± 0.07e
Percent normal (CI) 79% (71-87%) 88% (77-99%) 88% (78-96%)
* The normals in the ICM ap < 0.034; bp < 0.0001 series are different from those; c p < 0.008; dp < 0.039; e in the trophectoderm series. p< 0.003.

TABLE 5. DNA content of different genotype combinations comparing conceptuses with one part Igf2 ko with all the normals in the same litter (mean ± SD).*

Series n DNA ()
Fetal placenta Yolk sac Fetus
ICM
Normal 16 127.0 ± 33 98.5 ± 46 1 706 ± 472
Igf2 ko 18 106.3 ± 36 67.1 ± 46 1467 ± 376
Percent normal 84%a 68%a 86%a
Trophectoderm
Normal 9 130.2 ± 36 147.3 ± 33 1 736 ± 285
Igf2 ko 21 149.0 ± 36 146.6 ± 47 1714 ± 260
Percent normal 114%a 99%a 99%a

* The normals in the ICM series are different from those in the trophectoderm series. a Not significant.

This entry was posted in Growth Factor and tagged Genotypes, Growth Factor, Inner Cell Mass, Trophectoderm.