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Severe jaundice in early IVF pregnancy.

Jaundice in early pregnancy after in vitro fertilization (IVF) is extremely rare. We report a case of severe jaundice in an IVF treated patient, with a clinical picture similar to intrahepatic cholestasis of pregnancy (ICP). We suggest strategies to prevent similar cases in the future.

Adult↗

Bovine in vitro fertilization with frozen-thawed semen.

A procedure to obtain high and repeatable fertilization frequencies for bovine in vitro fertilization (IVF) with frozen-thawed sperm was developed. IVF frequency of in vitro matured oocytes was increased by a swimup sperm separation procedure (P=0.01) or treatment of sperm with the glycosaminoglycan heparin (P=0.0001), but the two factors did not interact (P=0.23). Heparin was the most important factor in increasing IVF frequencies. The fertilization frequency was not affected by the batch of oocytes used (P=0.38), but bull effects were present (P<0.05). Within a bull, the IVF system was highly repeatable and varied between trials no more than +/- 12% in fertilization frequency with an overall fertilization frequency of 299 379 (79%) on four trials over four bulls. In vivo matured oocytes fertilized in vitro were transferred to ewe or heifer oviducts. Morulae or blastocysts were recovered from ewes after four to five days, while conceptuses were present in the bovine after 25 days (diagnosed by ultrasound). Embryonic development from the IVF system either pre- or postimplantation was normal.

Journal Article↗

Detection of reactive oxygen species (ROS) and apoptosis in human fragmented embryos.

In human in-vitro fertilization (IVF)-embryo transfer, the in-vitro culture environment differs from in-vivo conditions in that the oxygen concentration is higher, and in such conditions the mouse embryos show a higher concentration of reactive oxygen species (ROS) in simple culture media. ROS are believed to cause damage to cell membranes and DNA fragmentation in somatic cells. This study was conducted to ascertain the level of H2O2 concentration within embryos and the morphological features of cell damage induced by H2O2. A total of 62 human oocytes and embryos (31 fragmented, 15 non-fragmented embryos, 16 unfertilized oocytes) was obtained from the IVF-embryo transfer programme. The relative intensity of H2O2 concentrations within embryos was measured using 2',7'-dichlorodihydrofluorescein diacetate by Quanti cell 500 fluorescence imaging and DNA fragmentation was observed with transmission electron microscopy and an in-situ apoptosis detection kit. The H2O2 concentrations were significantly higher in fragmented embryos (72.21 +/- 9.62, mean +/- SEM) compared to non-fragmented embryos (31.30 +/- 3.50, P < 0.05) and unfertilized oocytes (30.75 +/- 2.67, P < 0.05). Apoptosis was observed only in fragmented embryos, and was absent in non-fragmented embryos. Electron microscopic findings confirmed apoptotic bodies and cytoplasmic condensation in the fragmented blastomeres. We conclude that there is a direct relationship between increased H2O2 concentration and apoptosis, and that further studies should be undertaken to confirm these findings.

Apoptosis↗

Gamete intrafallopian transfer (GIFT).

Gamete intrafallopian transfer (GIFT), developed in 1984, was the result of further studies on in vitro fertilization (IVF). Since that time many nurses have worked in settings near in vitro fertilization centers and, therefore, have a basic understanding of the technology. An overview is given of the GIFT procedure to prepare nurses to advise and refer couples who may qualify for GIFT and to highlight the shift in the fertility program nurse coordinator's functions toward the positions of administrator and consultant.

Female↗

The ability of the hemizona assay to predict human fertilization in different and consecutive in-vitro fertilization cycles.

The objective of this prospective study was to examine the ability of the hemizona assay (HZA) to predict fertilization outcome of mature, pre-ovulatory oocytes under in-vitro fertilization (IVF) conditions. Since a large number of patients were evaluated over a long period, the power of the HZA to prognosticate fertilization results in the same and subsequent (consecutive) IVF cycles of those same patients was assessed. For IVF, only metaphase II oocytes were used. For the HZA, both fresh oocytes donated by patients at the time of IVF and oocytes recovered from surgically removed ovarian tissue (and salt-stored) were used, and bisected by micromanipulation techniques. Matching hemizonae were co-incubated either with spermatozoa from the patient (test) or from a fertile man (control) for 4 h. The number of spermatozoa tightly bound to the zona was counted. Patients (n = 112) were divided into two groups based on HZA results (expressed as HZA index or HZI): HZI > or = 30% (n = 72) and < 30% (n = 40). The patients with HZI < 30% had significantly lower fertilization rates in both the HZA-IVF cycle and in subsequent cycles compared to patients with HZI > or = 30% (P < 0.03). Linear discriminant analysis indicated the HZA to have a sensitivity of 84%, and positive and negative predictive values of 85 and 70% respectively, for prediction of fertilization outcome in a total of 233 cycles. It was concluded that the HZA is a good predictor of fertilization rate in vitro, and can be used in the IVF setting to supply additional clinical information in male-factor patients.

Female↗

In vitro maturation and fertilization techniques for assessment of semen quality and boar fertility.

The reliability of using different in vitro-derived measures of sperm quality to predict boar fertility was examined. On three occasions during a 20-wk period of breeding, special collections of the first sperm-rich fraction of the ejaculate from six boars were carried out. After in vitro capacitation procedures, three dilutions (5 x 10(5), 1.25 x 10(5), and 3.125 x 10(4) sperm/mL) of these semen samples were used in a standardized in vitro fertilization (IVF) test with oocytes recovered from prepubertal slaughterhouse ovaries and matured in vitro. Routine assessments of sperm motility, concentration, and morphology were also carried out for all collections used for AI during the 20-wk period. Semen from the same ejaculate, processed according to normal commercial practice using the AndroHEP extender, was used to inseminate equal numbers of recently weaned sows with either 3 x 10(9) or 2 x 10(9) total sperm, three times during the estrous period. Data from a total of 444 sows were used to determine boar fertility; between 12 and 54 sows were bred with each semen dose across the six boars. All measures of sperm fertilizing ability in vitro were different among boars (all P < .05) and use of different semen dilutions for IVF allowed further discrimination of apparent sperm quality among boars. The laboratory evaluation of semen collected during the period of breeding indicated effects of boar on ejaculate volume, total number of sperm per ejaculate, motility, and the percentage of sperm with normal morphology (all P < .01). Sperm dose used in AI had no effect on farrowing rate (80.7 vs 81.5%), but the lower AI dose resulted in a reduction (P < .05) in total numbers born (10.8 vs 10.0). For all three semen dilutions, estimated potential embryo production rate accounted for up to 70% of the variation in litter size obtained with 3 x 10(9) sperm per AI dose, and the number of sperm attached per oocyte was a major factor accounting for variation in litter size obtained with 2 x 10(9) sperm per AI dose. These IVF variables may, therefore, be effective indicators of boar sperm quality for use in AI. With 2 x 10(9) sperm per AI dose, the percentage of sperm with normal morphology also explained a large part of the variance in litter size born (R2 = .59), indicating that morphological characteristics are a useful measure of semen quality.

Animals↗

Embryonic development in vitro is compromised by the ICSI procedure.

The implantation rates achieved with intracytoplasmic sperm injection (ICSI) are equivalent to those with conventional in-vitro fertilization (IVF) but information on embryonic development in vitro after ICSI is scant. In this paper we compare blastocyst formation after IVF and ICSI; we have also investigated the effect of the ICSI procedure with internal control of extrinsic (including paternal) factors. The first series comprised cases of IVF treatment (n = 101) for tubal infertility and ICSI (n = 96) for male infertility. The proportions of embryos developing to the blastocyst stage was significantly lower after ICSI (8.9%, P < 0.001) than after conventional IVF (23.5%). In order to investigate the effect of the ICSI procedure in isolation, blastocyst formation was analysed in a second series of eight cases, in which sibling oocytes were non-selectively subjected to ICSI (n = 78) or IVF (n = 67) with spermatozoa from the same semen sample. It was found that 20% of ICSI embryos and 50% of IVF embryos formed blastocysts (P < 0.01), demonstrating that the ICSI procedure contributes to a reduced capacity for blastocyst formation in vitro.

Adult↗

Developmental competence of domestic cat embryos fertilized in vivo versus in vitro.

Development of in vitro-fertilized (IVF) cat embryos was compared to that of naturally produced cat embryos in vivo and in vitro. To obtain in vivo-fertilized embryos, queens were mated three times daily on the second and third days of natural estrus and ovariohysterectomized at 64, 76, 100, 124, or 148 h after the first copulation. Embryos were flushed from the reproductive tract, evaluated for developmental stage, and cultured. For IVF, oocytes from gonadotropin-stimulated queens were inseminated with electroejaculated cat sperm in Ham's F-10 and evaluated for fertilization (cleavage to > or = 2 cells) at 30 h. In vitro development of embryos fertilized in vivo (n = 109) and in vitro (n = 46) was evaluated every 24 h for up to 10 days. High-quality embryos recovered at 64, 76, 100, 124, and 148 h after the first copulation were typically 1 to 2 cells (13 of 20), 5 to 8 cells (18 of 28), 9 to 16 cells (14 of 24), morulae (15 of 21), and compact morulae (11 of 18), respectively, suggesting blastomere cleavage once per day in vivo after the first three rapid cell divisions. A similar developmental rate to the morula stage (p > or = 0.05) was achieved in vitro by embryos derived from both in vitro and in vivo fertilization. Additionally, the proportion (p > or = 0.05) of in vivo-generated embryos (2 to 16 cells) that developed to morulae (64 of 83; 77.1%) was similar to that of IVF embryos (28 of 46; 60.9%). However, none of the IVF embryos (0/46), but 70.6% (77 of 109) of the in vivo-produced embryos, achieved blastocyst formation in culture (p < or = 0.05). Furthermore, 66.2% (51 of 77) of these blastocysts exhibited zona hatching. Incidence of morula and blastocyst formation in the in vivo group was influenced by stage of the embryo at collection. Embryos that were at the 9- to 16-cell stage at recovery were more likely (p < or = 0.05) to achieve morula or blastocyst status and emerge from the zona pellucida than younger-stage counterparts. In summary, the in vivo and in vitro growth rate of cat embryos produced after natural mating was comparable to that of embryos fertilized and cultured in vitro. However, developmental ability to the blastocyst stage was superior for embryos produced in vivo after natural mating.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

Early history of in vitro fertilization.

Although in vitro fertilization (IVF) is used widely for a variety of purposes, it is often not appreciated how this technology was developed. A large number of experiments beginning in 1878 contributed to the first successful reports of IVF over 75 years later. The discovery of sperm capacitation in 1951 was central to the development of IVF technology, and it was rapidly followed by the first convincing reports of IVF in several species. The ability to fertilize oocytes in vitro has allowed major advances to be made into understanding the mechanisms involved in fertilization and early development, and IVF now supports reproductive biotechnology in animals and in humans. This article is a historical review of key experiments that helped to provide the basis for present day IVF procedures, placed into context with current practice.

Acrosome Reaction↗

A new test for the assessment of sperm-zona pellucida penetration: relationship with results of other sperm tests and fertilization in vitro.

The spermatozoa of some patients attending for in-vitro fertilization (IVF) fail to penetrate the zona pellucida in vitro. A test has been devised to identify these cases. It is based on the number of spermatozoa penetrating into the zona pellucida, which were counted after removing spermatozoa bound to the zona surface by vigorous aspiration of each oocyte through a narrow gauge (120 microns) glass pipette. The oocytes were collected from 197 patients undergoing IVF treatment with their own gametes; 79 with no oocytes fertilized and 118 with some oocytes fertilized. Sperm motility, morphology and DNA normality (acridine orange stain) were also measured. The relationships between sperm test results and IVF rate were examined by logistic regression. The proportions of penetrated zonae, normal sperm morphology and normal DNA were the most significant factors related to IVF rate in the whole group. Also, in patients with > or = 30 spermatozoa bound per zona pellucida or with normal sperm morphology > or = 30%, the proportion of penetrated zonae and normal DNA were most significant. Oocytes from 42 patients who had zero fertilization and low sperm-zona binding (average, 2.2 spermatozoa/zona pellucida) were re-incubated with normal donor spermatozoa: large numbers of spermatozoa bound (average, 88 spermatozoa/zona pellucida) and each zona was penetrated by at least one spermatozoon. In conclusion, the percentage of zonae penetrated was the variable most significantly correlated with IVF rate. Penetration of the zona was also strongly related to fertilization rates in patients without defects of sperm morphology and sperm-zona binding.(ABSTRACT TRUNCATED AT 250 WORDS)

Female↗

Improved in vitro fertilization and development by use of modified human tubal fluid and applicability of pronucleate embryos for cryopreservation by rapid freezing in inbred mice.

We examined in vitro fertilizability and development of 10 inbred mouse strains (C57BL/6J, C57BL/10, C57BL/10.D2/newSn, C57BL/10-Thy1.1, C57BL/10.Br/Sn, C3H/He, RFM/Ms, STS/A, BALB/c-nu and C.B-17/Icr), and the viability of frozen-thawed in vitro fertilized (IVF) embryos after embryo transfer (ET). In seven strains, fertilizability was significantly greater in modified human tubal fluid (mHTF) compared with modified Krebs-Ringer's bicarbonate solution (TYH medium). The TYH medium supported almost no fertilization in four strains. More than 80% of IVF embryos developed to the blastocyst stage by 120 h in potassium-enhanced simplex optimization medium (KSOM). Reciprocal fertilization between C57BL/6J and BALB/c-nu gametes in TYH medium yielded poor fertilization o f BALB/c-nu due to spermatozoal deficiencies. Increased concentrations of bovine serum albumin and spermatozoa during capacitation and Percoll washing did not drastically affect fertilization. The mHTF, but not TYH medium, supported BALB/c-nu spermatozoa penetration into the zona pellucida irrespective of capacitation media. In vitro fertilized embryos frozen-thawed rapidly were transferred to surrogate mothers at the two-cell stage. Compared with that of unfrozen controls, rapid freezing had no significant effect on fetus development except in C57BL/10.D2/newSn mice. These results suggest that mHTF medium is superior with respect to IVF of inbred mice, and that KSOM adequately supports in vitro fertilized embryo development in inbred mice. The data also indicate that rapid freezing of pronucleate embryos following IVF is suitable for cryopreservation and embryo banking of inbred mice and for the production of genetically modified mice.

Animals↗

A comparison of in vitro maturation and in vitro fertilization for women with polycystic ovaries.

OBJECTIVE: To establish the relative success of treatment by unstimulated in vitro maturation (IVM) of oocytes or stimulated in vitro fertilization (IVF) in women with polycystic ovaries undergoing assisted conception treatment. METHODS: The case-control study included 107 IVM and 107 IVF cycles matched for age and cause of infertility. In vitro maturation patients underwent transvaginal recovery of immature oocytes during an unstimulated cycle, in vitro oocyte maturation, and fertilization. Those in the IVF group underwent ovarian stimulation after pituitary suppression. Embryos were transferred in the same cycle in both groups. Main outcome measures included numbers of mature oocytes and embryos produced, and rates of implantation, pregnancy, live birth, and complications. RESULTS: In the IVM group after in vitro culture, 7.8 mature oocytes and 6.1 embryos were obtained per retrieval. With IVF, 12.0 mature oocytes (P <.01) and 9.3 embryos (P <.01) were obtained. The IVM pregnancy and live birth rates per retrieval were 26.2% and 15.9% compared with 38.3% and 26.2% for IVF (nonsignificant). The implantation rate of IVF-derived embryos was higher (17.1% versus 9.5%) than that for IVM (P <.01). There were 12 cases (11.2%) of moderate or severe ovarian hyperstimulation syndrome in IVF patients, compared with none in the IVM group (P <.01). CONCLUSION: Our results suggest that for women with polycystic ovaries who require assisted conception, IVM is a promising alternative to conventional IVF treatment.

Adult↗

Effects of general anaesthesia vs. sedation on fertilization, cleavage and pregnancy rates in an IVF program.

Anaesthetic management for oocyte retrieval may interfere with the results and success rate of an in vitro fertilization (IVF) program. This study was conducted to compare the effects of two different anaesthetic techniques (general anaesthesia versus sedation) used for oocyte retrieval on IVF outcome. For general anaesthesia we used a combination of remifentanil (Ultiva) with either propofol or isoflurane in hypnotic concentrations. For sedation the protocol included midazolam, diazepam or propofol according to clinical needs. In total, 202 women were enrolled in the study. 96 women opted for sedation and 106 for general anaesthesia. The number of collected oocytes was significantly higher with general anaesthesia (10.54+/-5.43 [mean+/-SD]) than with sedation (6.25+/-3.65, p<0.0001), whereas the number of fertilized oocytes was not different (4.70+/-3.57 vs. 4.23+/-2.90). There were no significant differences in cleavage and pregnancy rates. We therefore believe that remifentanil-based general anaesthesia without nitrous oxide is a suitable alternative to sedation and may be recommended for IVF oocyte retrieval if general anaesthesia is requested.

Anesthesia, General↗

An improved medium for long-term culture of human embryos overcomes the in vitro developmental block and increases blastocyst formation.

OBJECTIVE: To determine if a culture medium, designated CZB after the authors who first described it, which is supplemented with 0.11 mM ethylenediaminetetraacetic acid, 1.0 mM glutamine, 31.30 mM lactate, and 0.27 mM pyruvate and is lacking glucose for the initial stages of culture that overcomes the in vitro two-cell block of mouse embryos, can improve the rate of blastocyst formation of human embryos in long-term cultures and increase the pregnancy rate (PR) when used in a clinical in vitro fertilization (IVF) program. DESIGN: The study is in two parts. Initially, excess oocytes from IVF and gamete intrafallopian transfer patients were fertilized in vitro and then placed in long-term culture of either CZB plus 10% heat-inactivated human serum (32 zygotes) or Earle's balanced salt solution (EBSS) supplemented with 0.45 mM pyruvate plus 10% human serum (28 zygotes) to determine if CZB medium could enhance in vitro development and increase blastocyst formation when compared with EBSS. Subsequently, CZB or EBSS medium was used for short-term cultures of embryos in a clinical IVF program to determine if the use of CZB could increase the clinical IVF PR. SETTING: Private practice of one author (M.D.). PATIENTS: The excess oocytes were donated by couples not wishing to have cryopreservation. In the clinical trial, 49 couples presenting with tubal or male factor infertility and who had three or more fertilized zygotes were randomly assigned to one of the culture media being used. RESULTS: In long-term cultures, embryos were observed at 42, 66, 90, 114, and 138 hours after fertilization and scored for blastomere number, degree of fragmentation, and developmental arrest. When CZB- and EBSS-cultured embryos were evaluated over 138 hours, there was a significant increase in the number of CZB-cultured embryos reaching the blastocyst stage (56% versus 20%; P less than 0.009) and less fragmentation of CZB-cultured embryos (18.8% versus 50%; P less than 0.01). In short-term cultures, pronuclear stage embryos from patients undergoing IVF were cultured in CZB or EBSS for 24 hours, graded, and then used in embryo transfers. Of the 28 patients assigned to EBSS, 6 became pregnant (21.4%), and of the 21 assigned to CZB, 5 attained pregnancy (23.8%). These results were not significantly different. CONCLUSIONS: The use of CZB for the long-term culture of human embryos is highly beneficial and increases the rate of blastocyst formation, but its use in an IVF program does not increase the clinical PR.

Analysis of Variance↗

[Value of microfertilization for repeated in vitro fertilization failures: the role of female parameters].

UNLABELLED: Microfertilization technics as SUZI (sub-zonal insemination) can be indicated in cases of repeated in vitro fertilization (IVF) failure. Feminine parameters seem to play however an important role in optimalization of results. We studied 27 couples (32 IVF-SUZI cycles) who had previously presented 2 to 4 in vitro fertilization failures. These 32 cycles were divided in 2 groups according to women's age: group A < or = 35 and group B > 35 years. RESULTS: basal FSH levels were higher in group B (6.6 +/- 3.1 mIU/ml) in comparison to group A (3.7 +/- 1.5 mIU/ml). The amount of hMG necessary to accomplish ovarian stimulation was also higher in group B (39 +/- 21 ampules) than in group A (26 +/- 11 ampules). Maximal plasma estradiol levels were higher in group A (2,775 +/- 872 pg/ml) than in group B (1,824 +/- 559 pg/ml) such as the mean number of oocytes collected and micro-injected: 11.6 +/- 4.5 versus 4.7 +/- 2.2 in groups A and B, respectively. Eight pregnancies (44%), of which 7 were ongoing pregnancies, were obtained in group A. No pregnancy was obtained in group B. CONCLUSIONS: SUZI seems to be an available technic for treatment of repeated IVF failures; our results seem to indicate a decrease in SUZI results with age of the women (> 35 years old); they suggest the opportunity of a complete investigation of feminine parameters prior to each SUZI-IVF cycle.

Estradiol↗

The effect of a two-hour, room temperature incubation of human spermatozoa in TEST-yolk buffer on the rate of fertilization in vitro.

PURPOSE: To reassess the use of TEST-yolk buffer (TYB) in an in vitro fertilization (IVF) program by comparing fertilization rates achieved in a glucose-free cleavage medium by the standard IVF preparation of sperm versus a 2-h, room temperature incubation of sperm in TYB. METHODS: Oocytes collected for IVF were randomly split into two groups and inseminated with either TYB-treated sperm or IVF-prepared sperm. SETTING: Stanford Reproductive Endocrinology and Infertility Center. PATIENTS: Fifty couples undergoing IVF with at least 10 mature oocytes. MAIN OUTCOME MEASURES: Fertilization rates in vitro. RESULTS: Fertilization rates were significantly higher (p = 0.015) with TYB treatment. The average 2PN fertilization rate was 49.6% (188/379) for the IVF group and 57.4% (221/385) in the IVF with TYB group. CONCLUSIONS: A 2-h, room temperature incubation of sperm in TYB produces significantly higher 2PN fertilization rates as compared to standard IVF preparation of sperm in a current generation cleavage medium.

Culture Media↗

A sperm-zona pellucida binding test and in vitro fertilization.

Sperm binding to the zona pellucida was studied in 106 in vitro fertilization (IVF) patients. Oocytes that failed to fertilize in vitro were inseminated with a mixture of equal numbers of test and fertile donor sperm differentially labeled with fluorescein or rhodamine to control for variability in the sperm-zona pellucida binding capacity of oocytes. The ratio of the number of test and control sperm bound to four to six zonae pellucidae was significantly correlated with sperm morphology, viability, motility, motility index, and normal intact acrosomes in semen. The sperm-zona pellucida binding ratio was the most significant factor related to IVF rates by logistic regression analysis. But the proportions of sperm with normal morphology and intact acrosomes in semen also were significant. In patients with less than 30% of sperm with normal morphology, there was a highly significant relationship between IVF rate and sperm-zona pellucida binding and a weaker relationship with sperm morphology. In conclusion, the sperm-zona pellucida binding ratio test is useful for predicting sperm fertilizing ability in vitro, particularly in men with poor sperm morphology.

Cell Survival↗

Use of F1 progeny of HolsteinxZebu cross cattle as oocyte donors for in vitro embryo production and gene microinjection.

This study was designed to determine the possibility of using F1 crossbreed cattle (HolsteinxZebu) as donors of oocytes for in vitro fertilization (IVF) and for pronuclear gene microinjection into in vitro-produced embryos. In the first part of the experiment oocytes from Bos taurus (Holstein), Bos indicus (Zebu) and F1 crossbred Bos taurusxBos indicus (HolsteinxZebu) genotypes were inseminated with Bos taurus (Holstein) semen and were allocated for in vitro embryo production using conventional IVF procedures. No differences were observed on the in vitro maturation (IVM) rates between breeds (HolsteinxHolstein:85%, ZebuxHolstein:84% and ZebuxHolsteinxHolstein:88%). Holstein cows yielded the highest number of cumulus oocyte complexes (6.8 per ovary) for in vitro maturation, differing (P<0.05) from ZebuxHolstein and ZebuxHolsteinxHolstein F1 by 5.1 and 5.8, respectively. However, the Holstein breed also yielded the lowest percentage of cleavage (45.1 vs 71.9% for ZebuxHolstein and 65.1% for ZebuxHolsteinxHolstein). Of the 3 genotypes, the hybrid F1 breed was the most efficient source of oocytes for the production of embryos capable of reaching morulae and blastocyst stages (76/250; P<0.001). In the second part of the study, 599 oocytes from the F1 breed were fertilized in vitro, 1 group of 150 oocytes was used for the determination of the optimal pronuclear visualization period. The highest number of oocytes with 2 pronuclei was observed between 24 to 28 h after IVF (27 to 42%). The remaining 399 oocytes were microinjected with a gene construct bearing the bacterial lacZ gene as the reporter for gene expression. Survival of embryos to microinjection was 73.8%, and 45.5% of them (50/110) cleaved in culture. Of the microinjected embryos, 1 out of 50 showed beta-galactosidase activity. These findings indicate that a tropical crossbreed of cattle (ZebuxHolsteinxHolstein) can be used as a source of oocytes for IVF programs and gene microinjection studies.

Journal Article↗