Various ferroic orderings of triclinic tetrachloro-metallate dihydrate crystals.

In the triclinic crystals Rb(2)MnCl(4)·2H(2)O, Cs(2)MnCl(4)·2H(2)O and Cs(2)CaCl(4)·2H(2)O the ferroelastic domain structure has been observed for temperatures from 100 K to the dehydration point. On heating at a few degrees before the dehydration point the structure has been found to reorganize. On heating in Rb(2)MnCl(4)·2H(2)O and Cs(2)MnCl(4)·2H(2)O (but not in Cs(2)CaCl(4)·2H(2)O) a dielectric anomaly typical of a weak ferroelectric phase transition has been noted. The low-frequency dielectric dispersion in the low-temperature phase is attributed to the oscillations of the domain walls. The activation energy of this motion is 73 and 67 kJ mol(-1) in Rb(2)MnCl(4)·2H(2)O and Cs(2)MnCl(4)·2H(2)O, respectively. In the phase transition region the complex permittivity has been found to show oscillations as a function of temperature.

The role of calcium in DNA synthesis and development of mouse preimplantation embryos in vitro.

The effect of calcium upon embryonic growth was studied using cultured mouse preimplantation embryos. Both morphological development of the embryos and embryo DNA synthesis were shown to be dependent on the Ca2+ concentration in the medium in which the embryos were grown. Reduction of the calcium concentration below 10(-5) M completely blocked cell division and blastocyst formation in the cultured embryos, but only moderately inhibited embryo DNA synthesis. Trifluoperazine, a calmodulin antagonist, strongly inhibited the Ca(2+)-dependent DNA synthesis in the embryos. On the other hand, the drug only slightly affected the morphological development of the embryos. These results demonstrate that calcium independently affects two different aspects of the embryo development, i.e. DNA synthesis and cell division. It is suggested that the former effect is calmodulin-dependent, while the latter involves the calcium-dependence of metabolite transport through the cell membranes.

Birth of lambs after in vitro maturation, fertilization, and coculture with oviductal cells.

Control ovine oocytes matured and fertilized in vitro were transferred to intermediate recipient ewes. After 5 days, 59% of eggs were recovered. Thirty-one (38%) reached morula/blastocyst stage. Twenty-one embryos at the morula or blastocyst stage were transferred to six recipient ewes, resulting in five pregnancies, of which four were maintained. Nine lambs were born (43%). In the experiment, 72 ooctyes matured and fertilized in vitro were cocultured for 5 days with sheep oviductal epithelial cells. Thirty-one eggs (43%) developed to the noncompacted morula stage. Transfer of 26 embryos to 11 recipient ewes resulted in two pregnancies (18%). Two male lambs were born. The result indicates that the coculture of in vitro matured and fertilized ovine eggs with sheep oviductal epithelial cells throughout the preimplantation period is compatible with further development to term.

Cytogenetic analysis of experimental interspecies goat-sheep chimera.

Chromosomal analysis was carried out on blood lymphocytes, skin fibroblasts, and germinal cells of an interspecies goat-sheep chimera. This chimera was produced by aggregation of blastomeres of goat and sheep embryos. A cell chimerism 54,XX/60,XY was found in blood lymphocytes and skin fibroblasts. At birth the percentage of lymphocytes with karyotype 54,XX (sheep) amounted to 80% and with karyotype 60,XY (goat) to 20%. With age the percentage of lymphocytes with chromosome complement 54,XX increased, so that at 18 months it was 94% sheep and 6% goat. At the same age, in skin fibroblasts the percentage of cells with goat karyotype reached 25%. Analysis of germinal cells showed in spermatogonia the presence of only karyotype 60,XY and in primary spermatocytes of 29 autosomal bivalents and the sex bivalent XY.

Effect of polyamine limitation on DNA synthesis and development of mouse preimplantation embryos in vitro.

In-vitro treatment of preimplantation mouse embryos with spermine and spermidine biosynthesis inhibitor, methylglyoxal-bis-(guanylhydrazone) (MGBG), arrested embryo development at the 8-cell or morula stage. In addition, the embryo DNA synthetic rate, as measured by [3H]thymidine incorporation, was strongly inhibited. The inhibition of blastocyst formation and DNA synthesis by MGBG was readily reversible by an exogenous supply of spermine and/or spermidine to the culture medium. DL-alpha-Methylornithine or DL-alpha-difluoromethylornithine (alpha-DFMO), inhibitors of putrescine biosynthesis, had no effect on embryos cultured for 1 or 2 days, but on the 3rd day embryo DNA synthesis was significantly depressed in the presence of alpha-DFMO. These observations suggest that, during early development of the preimplantation mouse embryo, spermine and spermidine are involved in regulation of embryo growth and DNA synthesis. They may also indicate a role of putrescine at a later stage of mouse embryo development.

Deep freezing of horse embryos.

Fourteen horse embryos recovered non-surgically on Days 6-8 after ovulation (Day 0) were cooled slowly to - 35 degrees C (7 embryos) or - 40 degrees C (7 embryos) and stored in liquid nitrogen (- 196 degrees C) for 4-98 days. Surgical transfer of the thawed embryos to unmated recipient mares that had ovulated - 2 to + 1 days with respect to the embryo donors resulted initially in the establishment of 4 conceptuses. However, only one mare maintained her pregnancy to term.

Cryoprotection of day-4 mouse embryos by methanol.

Methanol was examined as a cryoprotective additive that permits the direct transfer of frozen--thawed Day-4 mouse embryos to foster mothers without dilution of the cryoprotectant. Methanol permeated the embryos rapidly, was not toxic and exerted a cryoprotective action. The highest level of survival (50%) of embryos in vitro was observed after equilibration in Medium PB1 containing 3.0 M-methanol, slow cooling (0.5 degrees C/min) to a temperature between -30 and -40 degrees C, rapid cooling (800 degrees C/min) and storage in liquid nitrogen (-196 degrees C), rapid warming (800 degrees C/min), and rapid dilution. A high rate of development in vivo to late-stage fetuses (up to 81%) was observed when cryopreserved embryos were transferred to pseudopregnant recipients immediately after thawing.