Multinucleated erythroid cells in blood of golden hamster embryos

Blood smears of 11 and 13-day-old embryos (20) and newborns (10) of golden hamsters were analysed. The smears were stained with brilliant cresyl blue in a moist chamber for 5--7 min. About 2--6 thousand cells were counted in 200 visual fields. By means of an ocular micrometer MOB-1 the diameters of 300 cells were measured and the curves on cell distribution were plotted according to the diameters. It was found that the blood of 11-day-old golden hamster embryos contained about 8% of binuclear and sixnuclear megaloblasts, and that of 13-day-old embryos--about 2.5% of binuclear and sixnuclear erythroblasts and megablasts of the second generation. In the bloood of newborn hamster polynuclear cells are absent.     

Dietary protein level and skeletal development in the golden Syrian hamster

The hamster was used as a model for investigating the effect of low, moderate, and high protein intake (12, 18, and 36% casein) on bone mineral content. Animals fed the low level of protein between 3 and 8 months of age had a reduction in the weight of all skeletal components measured, with the exception of the diaphyseal portion of the long bones. Diaphyseal weight and calcium remained significantly lower when expressed as a percentage of body weight. However, urinary calcium excretion was not lower than that of animals consuming an adequate protein intake. Ingesting a high protein diet resulted in a significant increase in urinary calcium excretion, and a reduced amount of both mineral and organic material in the diaphyses. We conclude that long-term consumption of a high protein ration led to the development of a mild osteoporotic condition in the hamster which was limited to the diaphyseal portions of the long bones.     

Cytokeratin filaments are present in golden hamster oocytes and early embryos

Light and electron microscope methods were used to study cytokeratin expression in the recently ovulated oocytes, fertilized eggs and early embryos from the golden hamster. Two cytokeratin polypeptides (Mr 51,000 and 58,000) were detected in oocyte lysates by immunoblotting using a polyclonal antiserum to prekeratin. In the oocyte, cytokeratin occurred as patchy aggregates consisting of short anastomosing 10-nm filaments that formed tight meshworks distributed throughout the cytoplasm. After fertilization the aggregates appeared to merge, becoming larger and concentrated at the cortical region. Prominent immunofluorescent fibrils were seen interconnecting the aggregates. In the 2-, 4- and 8-cell embryos, networks of cytokeratin filaments extended throughout the cortical and perinuclear regions, while aggregates progressively disappeared.     

Development of preimplantation embryos of the golden hamster in a defined culture medium

Eight-cell embryos were recovered from mated golden hamsters that had been superovulated with pregnant mare's serum gonadotropin (PMSG) and human chorionic gonadotropin (hCG). Embryos were cultured for 24 or 32 h in a defined medium (modified Tyrode's solution) designed for fertilization of hamster oocytes in vitro. This medium was supplemented in some experiments with amino acids (glutamine, phenylalanine, methionine and isoleucine) and with vitamins (Eagle's Minimum Essential Medium vitamin supplement). At the end of the culture period, the numbers of embryos developing to the blastocyst stage were recorded. In other experiments, the effects of varying the osmotic pressure (225, 250, 275 and 300 m0smol/kg) and the pH (6.8 and 7.4) of the culture medium on blastocyst formation were examined. A difference was found between the ability of early 8-cell embryos (approx. 54 h post-egg activation) and late 8-cell embryos (approx. 62 h post-egg activation) to develop in culture. In the unsupplemented culture medium, only 2% of early 8-cell embryos developed to the blastocyst stage compared with 22% of late 8-cell embryos. A marked effect of the four amino acids on development was found. In the presence of amino acids 36% of early 8-cell embryos developed into blastocysts (18-fold increase). The amino acids also increased the percentage of late 8-cell embryos that developed into blastocysts from 22% to 66%. These data suggest that an important metabolic change may occur in hamster embryos during a critical period at the 8-cell stage of development. No additional effect on development was observed when vitamins were included in the culture medium. No significant effect of either osmotic pressure of pH of the culture medium on development was found. When blastocysts formed from cultured 8-cell embryos were transferred surgically to pseudopregnant hamsters, about 25% developed into normal-looking fetuses and 5 normal-looking young were born, 4 of which have survived. These results represent an approach towards achieving complete preimplantation development of hamster embryos in vitro.     

Development of golden hamster embryos through the two-cell block in chemically defined medium

The effect of increasing the embryo:medium volume ratio on overcoming the hamster two-cell block was examined. Two-cell golden hamster embryos from each superovulated female were cultured in microdrops (estimated at 0.75 microliter) or 100 microliter macrodrops of chemically defined medium (modified Tyrode's solution [TLP] plus glutamine, isoleucine, methionine, phenylalanine, and taurine). In 11 trials (i.e., with embryos from 11 donors), 28.6% of 269 embryos developed to the four-cell stage in microdrops, whereas only 2 (0.7%) embryos developed in the macrodrops. When two microdrops were used to culture the two-cell embryos from each donor (n = 8), 17.8% of 304 embryos developed to four cells. Increasing the embryo:medium volume ratio further by culturing all of the embryos from each donor (n = 10) in single microdrops resulted in 53.1% of 397 embryos developing to four cells. Conditioning of the culture medium by these embryos could not be demonstrated. Increasing the embryo:medium volume ratio may protect against loss of some intracellular component essential for growth of early-stage hamster embryos. Alternatively, increasing this ratio may permit embryos to reduce the concentration of a substance detrimental to their growth. This work represents the first report of cleavage of hamster two-cell embryos in vitro. These findings are a significant step towards our goal of obtaining complete preimplantation developmental of hamster embryos in vitro and may be helpful for solving the in vitro developmental blocks in embryos from other species.     

Influence of estradiol on the capacity to produce antibodies during experimental amebiasis of the female golden hamster]

During experimental tissular amibiasis, the level of circulating antibodies, as detected by indirect immunofluorescence, is lower in female castrated golden hamsters who have been implanted with a pellet of oestradiol than in castrated control animals. Antibodies are first detected in the serum twenty four hours after infestation and their level becomes maximal near the fourteenth day.     

Localization of microfilaments during oocyte maturation of golden hamster

The localization and changes in microfilaments (MF) during golden hamster oocyte maturation were examined by an immunofluorescein method and confocal laser scanning microscopy (CLSM). We also studied the relationship between the changes in MF and oocyte nuclear and cytoplasmic maturation. During in vivo maturation, generalized submembranous MF were found initially which gradually became more prominent at the site of the first polar body extrusion. However, 43.7% of the in vitro matured metaphase 2 stage oocytes lacked the submembranous MF structure. This fact may partly account for the low fertilization rate of in vitro matured oocytes. MF were not found in the folicular oocytes cultured in cytochalasin-D-containing medium, and metaphase-like chromosomes were located at the center of the oocyte and first polar body extrusion did not occur. Twenty-five percent of the oocytes, which were arrested at meiosis by hypoxanthine, synthesized submembranous MF structure although the nuclear stage of these oocytes was germinal vesicle. These facts suggest that MF plays a role in nuclear behavior but there are some differences in the changes taking place within the nucleus and MF. MF may play a role in oocyte cytoplasmic maturation although the details of this have yet to be established. © 1995 Wiley-Liss, Inc.     

Complement increases in experimental Leishmania donovani infection of the golden hamster

Complement (C') levels in experimental visceral leishmaniasis were studied in the golden hamster. Using the total haemolytic assay of C' and the haemolytic diffusion plate assay for factor B, it was observed that the total haemolytic C' as well as factor B levels increased markedly starting one week after infection and remained high throughout most of the infection. A decline in C' level was noted toward the terminal stage of infection. The reason for the persistent high level of C' noted in this study was discussed.