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PubMed1995

Sex preselection by flow cytometric separation of X and Y chromosome-bearing sperm based on DNA difference: a review.

Recent research on the flow cytometry of sperm for the purpose of predetermining gender of offspring has led to a validated method to separate X from Y chromosome-bearing sperm for use with in vitro fertilization and embryo transfer, intratubal insemination or intracytoplasmic sperm injection. The basis for the method is the sex chromosome-specific marker, DNA, which is present in greater amounts in X-bearing sperm than in Y-bearing sperm of mammals. Sperm are exposed to the vital dye Hoechst 33342 which binds to the minor groove of the DNA helix. Flow cytometric sorting of the sperm using a laser as the excitation source results in populations of Y- or X-bearing sperm that are 85-90% pure. Several hundred offspring have been produced from swine, rabbits, sheep and cattle that confirm the predicted sex. The method is currently being applied to the commercial embryo market. The method is not likely to be used in conjunction with standard cattle or swine artificial insemination practice in its current form since only about 4 x 10(5) sorted sperm can be produced per hour of sorting. The technology has also been applied to human sperm for use by couples that are at risk to sex-linked disease expression in their offspring. Populations of human sperm have been sorted with X and Y purities of about 80% as confirmed by DNA probe technology and fluorescence in situ hybridization.

Cell Separation↗
PubMed1979

Use of albumin gradients for X and Y sperm separation and clinical experience with male sex preselection.

Semen samples obtained from 18 normal males and 37 husbands requesting male child preselection were separated on concentration gradients of human serum albumin. Separated semen obtained from the husbands was then used for artificial homologous insemination (AIH). A significant increase in the sperm motility, progressive drive, and percentage of Y-bearing sperm along with a decrease in the total sperm count and percentage of abnormal forms were observed in separated specimens. Fathers of three or more female children had a slightly smaller but statistically significant percentage of Y-bearing sperm in their semen samples than did normal males. Ten conceptions were achieved with separated semen. Seven pregnancies terminated in normal deliveries of five male and two female infants, one ended in a spontaneous abortion of a male fetus, and two patients are still expecting. The ratio of male to female conceptions in this small study parallels the ratio of Y to X sperm in the final specimen used for AIH.

Adult↗
PubMed1982

Sex preselection in mammals? Separation of sperm bearing Y and "O" chromosomes in the vole Microtus oregoni.

The two sex determining sperm populations of the vole Microtus oregoni were separated according to DNA content by use of flow sorting instrumentation. Although the sperm were not viable, they should be useful for addressing the question of haploid expression of genes linked to sex chromosomes and for efficiently searching for biochemical markers that differentiate the two populations.

Animals↗
PubMed2005

Preselection of sex of offspring in swine for production: current status of the process and its application.

It is estimated that as many as 30,000 offspring, mostly cattle, have been produced in the past 5 years using AI or some other means of transport with spermatozoa sexed by flow cytometric sperm sorting and DNA as the marker of differentiation. It is well documented that the only marker in sperm that can be effectively used for the separation of X- and Y-chromosome bearing spermatozoa is DNA. The method, as it is currently used worldwide, is commonly known as the Beltsville Sperm Sexing Technology. The method is based on the separation of sperm using flow cytometric sorting to sort fluorescently (Hoechst 33342) labeled sperm based on their relative content of DNA within each population of X- and Y-spermatozoa. Currently, sperm can be produced routinely at a rate of 15 million X- and an equal number of Y-sperm per hour. The technology is being applied in livestock, laboratory animals, and zoo animals; and in humans with a success rate of 90-95% in shifting the sex ratio of offspring. Delivery of sexed sperm to the site of fertilization varies with species. Conventional AI, intrauterine insemination, intra-tubal insemination, IVF with embryo transfer and deep intrauterine insemination are effectively used to obtain pregnancies dependent on species. Although sperm of all species can be sorted with high purity, achieving pregnancies with the low numbers of sperm needed for commercial application remains particularly elusive in swine. Deep intrauterine insemination with 50-100 million sexed boar sperm per AI has given encouragement to the view that insemination with one-fiftieth of the standard insemination number will be sufficient to achieve pregnancies with sexed sperm when specialized catheters are used. Catheter design, volume of inseminate, number of sexed sperm are areas where further development is needed before routine inseminations with sexed sperm can be conducted in swine. Cryopreservation of sex-sorted sperm has been routinely applied in cattle. Although piglets have been born from frozen sex-sorted boar sperm, freezing and processing protocols in combination with sex-sorted sperm are not yet optimal for routine use. This review will discuss the most recent results and advances in sex-sorting swine sperm with emphasis on what developments must take place for the sexing technology to be applied in commercial practice.

Animals↗
PubMed1989

The clinical relevance of sex selection techniques.

Clinical and laboratory attempts to alter the sex ratio require more complete and thorough study. Improved identification of Y-bearing sperm through chromosome evaluation rather than by F-body identification is critical to provide a more precise definition. The tentative conclusions stated below are based on an assessment of literature from which it is generally difficult to draw conclusions: 1. The timing of intercourse in relation to ovulation and subsequent fertilization appears to influence the sex ratio. More females are conceived when coitus occurs relatively close to ovulation, and more males are conceived when the sperm or egg is in the reproductive tract for a relatively longer time before conception. The influence of coital timing on the sex ratio is overall quite subtle and is not a practical method to alter the sex ratio for individual couples. 2. The use of ovulation-inducing medications slightly favors female offspring. A decrease in sex ratio of 5% to 10% has been shown in multiple studies. 3. Artificial insemination with fresh donor or homologous spermatozoa results in more male births with a reported 7% to 10% increase in the sex ratio. It appears that ovulation induction combined with artificial insemination cancels the respective influences of each on the sex ratio. 4. Sperm separation techniques using albumin (for selection of Y-bearing sperm) or Sephadex column filtration (for selection of X-bearing sperm) are the only techniques that have been reported to alter the sex ratio to a degree that is clinically relevant. Although clinical birth data are just beginning to accumulate, these methods appear to have a 70% to 80% success for selection of assumed Y-bearing sperm and a 75% to 80% success for selection of assumed X-bearing sperm. The validity of these results will remain questionable until fully detailed accounts are published and successfully repeated. Free-flow electrophoresis appears to achieve significant separation; however, the depressed postprocedure spermatozoa motility presently limits the usefulness of this procedure. 5. There is a potential to combine clinical and laboratory methods to maximize the efficiency of sex selection for interested couples. Modern methods to identify ovulation (e.g., urinary LH kits, ultrasonography) may help the timing of coitus for sex selection. Clomiphene citrate may enhance female sex preselection when Sephadex column filtration is also employed. 6. The priority of sex preselection in terms of medical, social, and demographic consideration remains to be determined. The avoidance of sex-linked genetic disorders is a reasonable and desirable goal.(ABSTRACT TRUNCATED AT 400 WORDS)

Cell Separation↗
PubMed1995

Social aspects of > 800 couples coming forward for gender selection of their children.

The social characteristics of 809 couples attending a sex preselection clinic have been studied. Their ethnic origins were: Indian 57.8%, European 32.0%, Chinese 3.6% and others 6.8%. The average number of boys and girls per family was 0.09 and 2.70 respectively for couples wanting a boy, and 2.46 and 0.14 for those wanting a girl. The average age of the wives was 34.0 years. These figures were not significantly different in any ethnic subgroup. Out of all the couples, 80.6% stated that they would have had another baby even had sex preselection not been on offer; 37.5% of the couples interviewed have been treated so far. The figures among those treated are substantially the same as those for the whole group. Asian and Middle Eastern couples overwhelmingly wanted boys, whereas European couples showed a slight preference for girls. These results suggest that, given certain guidelines, sex selection is unlikely to lead to a serious distortion of the sex ratio in Britain and other Western societies, but may need careful monitoring in other parts of the world.

Adult↗
PubMed1984

A prospective study of the preselection of the sex of offspring by timing intercourse relative to ovulation.

The relationship between the sex of offspring and the time interval between coitus and ovulation/fertilization has been prospectively investigated in 33 pregnancies using the rise in luteinizing hormone in the early morning urine, the peak cervical mucus symptom, and the shift in basal body temperature as indicators for ovulation. Reference to the peak cervical mucus symptom showed a significant association of conception of a male child with longer intervals (greater than 2 days) between coitus and fertilization (P less than 0.03). However, while a similar trend for male conceptions was evident when the duration of sperm survival was determined by reference to each of the other two indicators of ovulation, the relationship was not significant. The results clearly refute the theory that intercourse close to ovulation favors male conceptions. While the findings are consistent with the contrary theory, it may be premature to conclude that a male child is more likely to be conceived if coitus takes place several days before ovulation.

Adult↗
PubMed2006

In vitro production of cat blastocysts of predetermined sex using flow cytometrically sorted semen.

Sex preselection in cats can have applications for both breeding purposes and as an experimental model for endangered felids. The present study examined the ability to produce cat embryos from in vitro fertilization (IVF) of in vitro matured (IVM) cat oocytes with flow cytometrically sorted spermatozoa and to verify the sex of the embryos obtained from sexed spermatozoa by PCR. In the first experiment, a total of 224 oocytes were fertilized with spermatozoa from six ejaculates sorted without sex separation. The sorting process did not influence the cleavage rate (sorted 44.0% versus unsorted 46.1%), day 6 morula-blastocyst rate (sorted 26.6% versus unsorted 29.6%) and day 7 blastocyst rate (sorted 16.5% versus unsorted 16.5%). In the second experiment, a total of 84 IVM oocytes were fertilized with sorted X- and Y-chromosome bearing spermatozoa from four ejaculates in order to obtain embryos of preselected sex. Embryonic sex determination by PCR revealed that 21 out of 24 embryos reaching morula/blastocyst stage (87.5%) were of the desired sex. In particular 12 out of 14 embryos (85.7%) derived from X-bearing spermatozoa were female and 9 embryos out of 10 (90%) derived from Y-bearing spermatozoa were male. Our results show, for the first time, that X- and Y-chromosome bearing spermatozoa sorted by high-speed flow cytometry can be successfully used in an IVM-IVF system to obtain cat embryos of a predetermined sex.

Animals↗
PubMed2006

Birth of twins after in vitro fertilization with flow-cytometric sorted buffalo (Bubalus bubalis) sperm.

Flow-cytometric sorting of mammalian sperm for production of offspring with the desired sex is one of the most important new biotechnologies available for livestock industry. The objectives of this study were: (i) to sort the sperm into X- and Y-enriched populations and (ii) use the sorted sperm for in vitro fertilization (IVF) to produce sex-preselected embryo and offspring. The results revealed that the accuracy of sorted X- and Y-sperm was 94% and 89%, respectively. There was a decrease in blastocyst development rate in IVF with sorted sperm comparing to unsorted sperm, but the percentage of blastocysts on D6-D8 was not statistically different. Transplantation of the presumed X-embryos derived from IVF into a recipient resulted in the birth of female twins. These results indicated the feasibility of sperm sorting by flow cytometry and in vitro production of sex-preselected embryos and offspring in buffalo.

Animals↗