Embryo culture in explanted oviducts in mice and cattle

Developmental block of early embryos is due to the lack of some components in the culture medium and/or caused by inappropriate environmental conditions for embryonic development. It was shown in our experiments that the development of mouse and bovine embryos under the influence of oviducts in vitro can provide us with a model to analyze the oviductal factors that promote embryonic development. In the first experiment, it was shown that mouse zygotes developed to the blastocyst stage when a coculture system with ampulla was applied, and the duration of embryo coculture significantly affected the further development of embryos. In the second experiment, it was shown that the proportion of blastocysts of cleaved ova obtained after coculture with mouse ampulla was significantly higher than that obtained after coculture with a granulosa cell monolayer or culture without cells.

Growth retardation in rats whose growth hormone gene expression was suppressed by antisense RNA transgene

We produced four transgenic founder rats (F0) by introducing into rat embryos a fusion gene, which consisted of rat growth hormone (GH) promoter containing with four copies of thyroid hormone response element (TRE) and antisense cDNA sequences for rat GH. This transgene promoter directed 2.8-fold stimulation of CAT gene expression in transfected GH3 rat pituitary tumor cells compared with the rat GH promoter alone. Two of four transgenic rats expressed antisense RNA in the pituitary. Transgenic offspring (F1) from each founder rat exhibited dwarfism at as early as 3-4 weeks of age, and they exhibited approximately 70-85% reduced growth rate compared with their nontransgenic littermates over 56 weeks of observation. Plasma rat GH concentration was approximately 40-50% lower in transgenic F1 rats compared to their nontransgenic littermates. In these experiments, the pituitary hormone expression controlled in a complex manner was shown to be repressed by the antisense RNA transgene. Furthermore, the suppression of gene expression could be achieved by antisense RNA transgene in the rat as well.

Developmental ability of enucleated bovine oocytes matured in vitro after fusion with single blastomeres of eight-cell embryos matured and fertilized in vitro

Single blastomeres from eight-cell stage bovine embryos matured and fertilized in vitro were electrically fused with enucleated oocytes matured in vitro. In experiment 1, The percentage of these reconstituted embryos developed to the two- to eight-cell stage 48 hr after electrofusion was increased when both the eight-cell embryos and the enucleated oocytes were derived from oocytes cultured with granulosa cells (14% vs. 38%). In experiment 2, the relationship between activation of oocytes and developmental ability of reconstituted embryos was examined. Although both ethanol and electrical stimulation efficiently induced parthenogenetic activation of oocytes matured in vitro for 26-28 hr (ethanol, 89%; electrical stimulation, 73%), the ratio of the second polar body extrusion differed (80% vs. 22%). Ethanol-treated enucleated oocytes, however, were not significantly different from the early cleavage of the reconstituted embryos 48 hr after electrofusion (nontreated, 38%; treated, 43%). In experiment 3, reconstituted embryos at the two- to eight-cell stage 48 hr after the electrofusion were cocultured with granulosa cells for 6-7 days. Of 69 embryos, one developed to a morula and three developed to blastocysts.

Development of hamster one-cell embryos recovered under different conditions to the blastocyst stage

One-cell stage embryos, recovered from superovulated golden hamsters (8 to 12 weeks of age) 12 hours after egg activation, were cultured in HECM-1 medium at 37 degrees C and 5% CO(2) in air. The culture conditions investigated were the time and temperature required for embro recovery, the pH shift of the washing medium, and the oxygen concentration of the gas phase during and after embryo recovery. Each condition was assessed by the developmental efficiency of the embryo as determined by morphological criteria. As the time required for embryo recovery was reduced, the developmental rates of the embryos were improved: 2.3% (3 128 ) 26.9% (35 130 ) at 5 and 3 minutes, respectively, as determined by the number of embryos developed to the blastocyst stage. No blastocysts were obtained when more than 10 minutes were required for embryo recovery. As the oxygen concentration was reduced from 40 to 20% or to 5%, rather high developmental rates were obtained even when the time required for embryo recovery was prolonged: 6.9% (9 130 ) and 21.7% (28 129 ) of the embryos developed to the blastocyst stage when they were recovered under 5% oxygen within 10 and 5 minutes, respectively. Neither the temperature during embryo recovery (37 degrees C and 25 degrees C) nor the pH shift (pH 7.22 to 7.52) of the washing medium used in embryo recovery procedures influenced the development of the embryos. These findings suggest that the developmental block in hamster embryos may involve oxidative stress, which may result from exposure to high oxygen concentration and light during the manipulation of oocytes and embryos.

Embryo sex selection by a rat male-specific antibody and the cytogenetic and developmental confirmation in cattle embryos

Embryos of mouse, rabbit, goat, sheep, and cattle were separated into 2 groups on the basis of their morphology when incubated with a male-specific antibody (qualified here as the H-Y antibody) prepared from newborn rat testis. When morula-stage embryos were cultured in the presence of this H-Y antibody, the development of roughly one half of the embryos was arrested at that stage, whereas the other half continued to develop to the blastocyst stage. The developmentally arrested group of embryos resumed their development into blastocysts when cultured in antibody-free medium. Eighty to 90% of cattle embryos whose development was unaffected by the antibody were shown to possess a female karyotype (XX), and close to 80% of those embryos whose development was arrested possessed a male karyotype (XY). Cattle embryos whose sex had been presumptively identified by development in the presence of the H-Y antibody were cryopreserved and transferred, and the sex of the calves was examined. The overt sex of the young born from sexed embryos was found to be the same as that determined by chromosomal analysis.

Effects of low molecular weight oviductal factors on the development of mouse one-cell embryos in vitro

The relationship between the oviduct and embryo development in the mouse was investigated and the period at which the influence of oviduct can be concerned in the development of mouse embryos in vitro was identified. In addition, the relative molecular weight of oviductal factors that promote embryo development was demonstrated. Mouse zygotes developed to the blastocyst stage when co-cultured with ampulla. The period of embryo co-culture significantly affected the further development of the embryos. Fewer one-cell embryos co-cultured with dissected ampullae for less than 24 h developed to blastocysts than those co-cultured for more than 28 h (P < 0.001). A high percentage of embryos co-cultured with ampullae after 24 h of culture in vitro developed to the blastocyst stage, which suggests that the influences of ampulla on the development of mouse embryos are restricted to a specific period at the two-cell stage (about 55-56 h after hCG injection) in vitro. Mouse ova that were cultured in media conditioned by ampullae could also develop to the blastocyst stage. The fractionated medium that contained low molecular weight fractions was more effective (P < 0.001) on the development of embryos to the blastocyst stage than that containing high molecular weight fractions. These results suggest that the low molecular weight oviductal factors play an important role in the development of mouse embryos at a certain critical age in vitro.

Cryoprotective effect of polyols on rat embryos during two-step freezing

The cryoprotective effect of polyols on rat embryos was measured after two-step freezing, and the mechanism of action of polyols on embryo survival was examined. Rat embryos frozen in solution of polyol by two-step method at the morula stage showed higher survival than that obtained using DMSO. As the number of hydroxyl groups increased, the cryoprotective effect of the polyol increased. However, this was true only when the additive could permeate the cell membrane. Of the additives tested, four or five carbon polyols were most effective at concentrations of 0.3 or 1.0 M than two, three, six, or seven carbon polyols. The highest survival rate was obtained with adonitol, which yielded 83% embryo survival at 1.0 M and 67% even at 0.3 M. Embryos frozen in 0.3 M adonitol and transferred directly into foster mothers without any dilution of the additive after thawing developed into live young. During slow cooling below -40 degrees C, embryonic blastomeres exhibited cell fusion only in the presence of adonitol. These findings suggest that one cryoprotective action of polyols is that the hydroxyl groups act both on the cell surface and the cytoplasm to stabilize the bound water on the embryonic membrane, and that the length of the C-chain determines the permeability of the membrane to the additive.

Sexing of rat embryos with antisera specific for male rats

Male-specific antigenicity (H-Y antigen) of rat embryos has been examined, and the feasibility of sexing rat embryos by use of H-Y antibodies has been studied. Rat H-Y antisera were produced by immunization of female Wistar rats with a homogenate of testes from male Wistar neonates. Male specificity of the antiserum (H-Y antibody) was determined by retention of cytotoxicity to male epidermal cells after absorption with female cells. After cultivation of rat embryos for 5 to 6 hr in the presence of antibody, half of the embryos were arrested at the morula stage. However, these embryos developed into blastocysts after removal of the antiserum, and then they grew into male young in recipient foster mothers. Eighty percent of the embryos that developed to blastocysts in the presence of the antiserum grew into female young.

Separation of mounting-inducing pheromones of vaginal mucus from estrual heifers

There is evidence that mucus of the female bovine genital tract contains pheromones that induce physiological and behavioral responses in other animals. To study these pheromones, vaginal mucus was collected from heifers either at estrus or during diestrus. The mucus was then applied to the hindquarters of the same animal during diestrus or to the hindquarters of herdmates during diestrus. The behaviors of the treated animal and its herdmates were then observed. To attempt to isolate the mounting-inducing substance, mucus was dialyzed or separated on ion-exchange resins. Diestrous heifers to which their own estrual mucus has been applied were nearly always mounted by herdmates (P less than .01). But, heifers to which another's estrous mucus had been applied were not mounted. This suggests that vaginal mucus contains not only estrus-related pheromones, but also individual distinctive odors. The dialyzable fraction of vaginal mucus and the neutral fraction, prepared by ion-exchange chromatography of the dialyzable solution of vaginal mucus, had a mounting-inducing activity on the herdmates, as did the application of an animal's own vaginal mucus. These findings suggest that mounting-inducing pheromones are relatively low molecular weight, neutral substances.

Full-term development of bovine follicular oocytes matured in culture and fertilized in vitro

Follicular oocytes were cultured for 28h in vitro and 91% of the oocytes reached the the second metaphase in culture. The penetration rate after insemination in vitro using frozen-thawed spermatozoa was 81%. After cultivation for 48h in vitro, 18% of the in vitro fertilized oocytes developed to the three- to four-cell stages and 21% of these developed to the six- to eight-cell stages. Following in vivo culture in the rabbit oviduct, 18% of six- to eight-cell and 5% of three- to four-cell embryos developed to the blastocyst stage. To confirm the full developmental competence, 11 blastocysts were transferred to recipient cows, and six (55%) cows became pregnant or delivered calves.

Structural analysis of repetitive DNA sequences in the goat growth hormone gene region

Two clones that contain goat growth hormone (gGH) genes were isolated from goat genomic library using goat growth hormone cDNA as a probe. One clone CgGH contained gGH1 gene, and another clone, EgGH, contained gGH2 and gGH3 genes. The clone EgGH contained 491 bp inserted sequence, just upstream of the gGH3 gene, which was not present in the clone CgGH. From the sequencing data of the flanking regions of these gGH genes, short interspersed repetitive sequences (SINES) were found. Four SINES's existed in the CgGH clone and eight SINES's existed in the EgGH clone. The number of the repetitive DNA sequences in the goat genome was estimated about 10(2) copies from the analysis of the reassociation rate. As the number of gGH genes (gGH1, gGH2, and gGH3) per genome was different among individual goats, DNA fragments containing gGH1 gene, and that containing gGH2 and gGH3 genes, were estimated to be allelic on the goat chromosome.

Fertilizing competency of multiple ovulated eggs in the domestic fowl (Gallus domesticus)

Fertilizing competency of multiple ovulated eggs in the domestic fowl was examined by fertilization in vitro and early development in culture. Normal laying hens (White Leghorn) were treated with 75 IU of PMSG for 7 days followed by injection of anterior pituitary extracts from chickens (CAPE). Ovulation began to occur 7.5 h after injection of CAPE. These hens ovulated 1-7 ova but some premature ovulation of GV stage ova were observed. In vitro fertilization of the multiple ovulated ova was examined by inseminating 10(6)-10(7) sperm onto the germinal disks in m-Ringer's solution. The gamete or zygote nuclei were detected by DNA specific fluorescence using DAPI (4',6'-diamidino-2-phenylindole) in the histological section prepared from the germinal disk. Process of fertilization was examined in the eggs incubated for 4 h after insemination in DMEM + liquid albumen at 41 degrees C under the atmosphere of 5% CO2 in air. Fertilization rate of the total multiple ovulated eggs was 55% (11/20), in which 90% (9/10) and 10% (1/10) in the eggs recovered 7.5-8.5 h and 9.0-9.5 h after CAPE injection were obtained, respectively. Normal pronuclei were formed in five eggs of those recovered 7.5-8.5 h after CAPE injection. Early development after fertilization in vitro was also examined by incubation for 12 h in DMEM + liquid albumen at 41 degrees C under the atmosphere of 5% CO2 in air. Although development in vitro was delayed compared to that in utero condition, normal development was observed in naturally and multiple ovulated eggs.(ABSTRACT TRUNCATED AT 250 WORDS)

Early nuclear events of in vitro fertilization in the domestic fowl (Gallus domesticus)

In vitro fertilization in the domestic fowl (Gallus domesticus) was investigated by observation of the early nuclear events. Ova retrieved from the fimbria following ovulation were inseminated in vitro with 10(6)-10(7) spermatozoa in Dulbecco's modified Eagle's medium (DMEM) for 10 min and then further incubated in DMEM + albumen for 1, 2, 3, or 4 hr. These eggs were histologically examined by epifluorescent microscopy after staining with 4',6'-diamidino-2-phenylindole (DAPI). Nuclei of spermatozoa at various stages of transformation were observed in the ova incubated for 1-3 hr. Close pairing of two pronuclei, presumed to be male and female juxtaposition, was detected in ova incubated for 4 hr. These data provide direct evidence for the in vitro fertilization of fowl eggs and suggested that the early process of in vitro fertilization is comparable to that of in vivo fertilization.

Ooplasmic transfusion: prophase germinal vesicle oocytes made developmentally competent by microinjection of metaphase II egg cytoplasm

Approximately one fourth of all human oocytes collected for in vitro fertilization are of immature origin. Even when these oocytes undergo nuclear maturation, fertilization, and cleavage in vitro, transfer of such embryos rarely results in pregnancy reaching delivery. We hypothesized that human embryos derived from prophase I oocytes were developmentally incompetent because they lacked a factor(s) found in in vivo matured oocytes. Using micromanipulation techniques in monkeys, we removed ooplasm from metaphase II oocytes and injected it into prophase I oocytes. After nuclear maturation, oocytes were transferred to the fallopian tube for fertilization. After ooplasmic transfusion, prophase I oocytes resulted in a delivery rate of 13%. When metaphase II ooplasm was heated or exposed to ribonuclease A before microinjection into prophase I oocytes, it lost effectiveness in conferring developmental competence.

Motility and fertilizing ability of rat epididymal spermatozoa washed by a continuous gradient of Percoll

Removal of epididymal fluids from epididymal sperm suspension is an important step for the study of sperm motility, capacitation, and the acrosome reaction. The technique of washing should minimize damage to viable spermatozoa but at the same time efficiently remove debris, non-sperm cells, and biological fluids. We examined sperm motility and fertilizability in vitro of rat epididymal spermatozoa after washing with Percoll continuous gradient. Nine milliliters (ml) of 50% N-2-hydroxyethylpiperazine-N1-2-ethanesulfonic acid (HEPES) buffered Percoll solution was centrifuged at 20,000 g for 45 minutes to form a continuous gradient. One hundred to 300 microliters of sperm suspension was loaded onto the surface of the gradient and centrifuged at 150 g and 1,500 g for 10 minutes. Two main layers of spermatozoa were formed, one of high (lower layer) and one of low (upper layer) motility. At centrifugation 1,500 g, the sperm density and motility in the lower layer were greater than at 150 g. Spermatozoa from both layers at 150 g and at 1,500 g were diluted with modified Krebs-Ringer's bicarbonate solution (mKRB) and preincubated for 5 hours. Superovulated eggs collected from 21-25-day-old Wistar strain immature rats were introduced into the preincubated sperm suspension for insemination and fixed 5-5.5 hours later for observation of fertilization. Spermatozoa from both layers, 150 g and 1,500 g, showed the same fertilizability in vitro as control spermatozoa. From these results we conclude that Percoll gradients can be used for washing rat epididymal sperm for the study of sperm physiology including fertilization.