Establishment of Guinea pig fetal fibroblast cells and their biological evaluation before and after cryopreservation were the main purposes of this study. After determination of the proper age of pregnancy by ultrasonography, 30 days old fetuses of Guinea pigs were recovered. Their skins were cut into small pieces (1 mm2) and were cultured. When reaching 80–90% confluence, the cells were passaged. Cells of the second and eighth passages were cultured in 24-well plates (4 × 104 cells/well) for 6 days and three wells per day were counted. The average cell counts at each time point were then plotted against time and the population doubling time (PDT) was determined. Then, vials of cells (2 × 106 cells/mL) were cryopreserved for 1 month and after thawing, the cell viability was evaluated. The PDT of the second passage was about 23 h and for the eighth passage was about 30 h. The viability of the cultures was 95% in the second passage and 74.5% in the eighth passage. It was shown that the Guinea pig fetal fibroblast cell culture can be established using the adherent culture method while, after freezing, the viability indices of these cells were favorable.

Background Hamster is widely used as an experimental model in the study of reproductive system. However, pregnancy diagnosis and aging always have been a challenge. ultrasonography have been used in diagnosis of pregnancy in some small laboratory animals, such as rabbits, rats, and mice. Current study describes use of trans-abdominal ultrasonography for pregnancy diagnosis and fetal age estimation in golden hamster. Furthermore, a macroscopic examination was performed to evaluate the embryonic vesicle diameter, crown-rump length, and fetal head diameter. Ten adult female golden hamsters were selected and maintained under controlled light conditions (14 h light/10 h darkness). The estrous cycle was synchronized using eCG and hCG. During estrous (18 h after hCG injection), the hamsters were naturally mated. After seven days of mating, the hamsters were examined daily for pregnancy diagnosis and aging with an ultrasound scanner equipped with an 8.5-MHZ linear probe. On each day of the experiment, at least one of the pregnant hamsters was euthanized and dissected for macroscopic fetal measurements using a digital caliper. Results The gestational sac and crown-rump length were identified and measured by ultrasonographicly on day 7 of pregnancy and head could be visible after day 10 of gestation. Statistical analysis revealed that the ultrasound estimation of gestational age was significantly correlated with the actual age of the fetus (r = 0.98; p < 0.05). Conclusions Real-time ultrasound can be used for the diagnosis of pregnancy and estimation of fetal age in golden hamster from day 7 of gestation.