Effects of pH on the migration of X and Y sperm

The History and Prospects of Rabbit Sperm Sexing

Sperm sex selection is a longstanding challenge in the field of animal reproduction. The cuniculture industry, in particular producers of males or females for breeding purposes, would greatly benefit from the pre-selection of the offspring's sex. This review article overviews the current and future developments in rabbit sperm sexing technologies, as well as the implications of implementing these methodologies in cuniculture. The first attempts of sperm sexing were performed in rabbits; however, a both efficient and cost-effective methodology was not yet developed for this species. Those included sperm sexing according to differences in sperm density, surface electric charge, pH susceptibility, antisera reaction, and flow cytometry. Separation by flow cytometry has proven to be efficient in rabbits, yielding fractions with approximately 81% and 86% purity for X- and Y-sperm, respectively. However, it is not cost-effective for cuniculture and decreases sperm quality. The advantages, limitations, and practical considerations of each method are presented, highlighting their applicability and efficiency. Furthermore, herein we explore the potential of immunological-based techniques that overcome some of the limitations of earlier methods, as well as recent advancements in sperm sexing technologies in other animal models, which could be applied to rabbits. Finally, the challenges associated with the development and widespread implementation of rabbit sperm sexing technologies are addressed. By understanding the advantages and limitations of existing and emerging methods, researchers can direct their efforts towards the most promising directions, ultimately contributing to a more efficient, profitable, and sustainable cuniculture.

New Biological Insights on X and Y Chromosome-Bearing Spermatozoa

A spermatozoon is a male germ cell capable of fertilizing an oocyte and carries genetic information for determining the sex of the offspring. It comprises autosomes and an X (X spermatozoa) or a Y chromosome (Y spermatozoa). The origin and maturation of both X and Y spermatozoa are the same, however, certain differences may exist. Previous studies proposed a substantial difference between X and Y spermatozoa, however, recent studies suggest negligible or no differences between these spermatozoa with respect to ratio, shape and size, motility and swimming pattern, strength, electric charge, pH, stress response, and aneuploidy. The only difference between X and Y spermatozoa lies in their DNA content. Moreover, recent proteomic and genomic studies have identified a set of proteins and genes that are differentially expressed between X and Y spermatozoa. Therefore, the difference in DNA content might be responsible for the differential expression of certain genes and proteins between these cells. In this review, we have compiled our present knowledge to compare X and Y spermatozoa with respect to their structural, functional, and molecular features. In addition, we have highlighted several areas that could be explored in future studies in this field.

Effect of the pH in the enrichment of X or Y sex chromosome-bearing sperm in bovine

Background and Aim:

Studies have shown that the pH of the vagina during the course of fertilization may influence the migration of X- and Y-bearing spermatozoa and thus leading to skewness in the sex of the offspring. Hence, this study was carried out to check the effect of the pH in the enrichment of X or Y sex chromosome-bearing sperm in bovine (Bos indicus).

Materials and Methods:

To check the effect of pH in the enrichment of X or Y sex chromosome-bearing sperm in bovine, we used buffers of various pH ranging from 5.5 to 9.0 for swim-up procedure of sperm sample and collected upper and bottom fraction from the same buffer and checked the abundance of X- and Y-bearing spermatozoa by droplet digital polymerase chain reaction using X- and Y-chromosome-specific DNA probe.

Results:

The abundance of X- and Y-bearing spermatozoa was not differed significantly in either of the fraction collected.

Conclusion:

Thus, it appears to be unlikely that an immediate impact of pH on sperm can be a solitary impact on the sex of offspring in bovine.

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)

Preconceptional selection of fetal sex

Background information is given on postconceptional and preconceptional methods of selecting fetal sex. Among the preconceptional methods presented are treatment of the sperm to isolate either the X or the Y chromosome, timing of insemination and the effect of ionic concentrations in the woman's body as controlled by the dietary intake of minerals. The authors studied 281 couples, 21 of whom were later excluded, who adhered to a diet specific in its amounts of calcium, magnesium, sodium and potassium. This dietary method of preconceptional selection of fetal sex resulted in the anticipated outcome in about 80% of the cases.

The frequency of Y chromatin-positive spermatozoa during in vitro penetration tests under various experimental conditions

Complete analysis were carried out on the semen of 55 subjects. The semen was then investigated by using the fluorescent microscopic technique to determine the percentage proportion of Y chromatin-bearing spermatozoa. After staining with quinacrine mustard, an average Y chromatin frequency of 48.2% +/- 2.9% was recorded. With this spermatozoal material, 139 in vitro penetration tests were carried out with cervical mucus. After penetration there was a small, but statistically significant, increase in the percentage of Y spermatozoa (to 52.7% +/- 3.8%). The figures thus recorded were then correlated under variable experimental conditions in addition to variable semen parameters. The ratio of X:Y spermatozoa was related to the duration of the penetration tests, varying temperatures during the penetration, varying acid values of semen and cervical secretion, and also to the value of sperm motility in the semen analysis and to cervical factors. None of the above variables had any measurable influence on the percentage distribution of X and Y spermatozoa during in vitro penetration.

X to Y spermatozoal ratio in normal and oligozoospermic human semen and its relationship to fertility parameters

The ratio of X to Y spermatozoa in normo and oligozoospermic human semen is established with a fluorescent technic using quinacrine. The relationship between concentration of X and Y spermatozoa to factors that potentially control the fertilizing ability of spermatozoa (i.e. sperm count, vitality, motility and morphology) is analyzed. Out of a total of 44 samples (22 normo and 22 oligozoospermic samples) a ratio of 1:1 in X to Y spermatozoa is found in both groups. The frequency of X to Y spermatozoa in the evaculate is not related to sperm count. It is also independent from morphology, motility, and vitality of spermatozoa.

Enrichment of X-spermatozoa and in vitro penetration through cervical mucus

Using the Sephadex Gel-filtration method (Steeno - 1975) we carried out a review of the data on the possibility of enriching X-spermatozoa. The testing procedure followed consisted of determining Y-chromatin positive spermatozoa after staining with quinacrine-mustard. We were able to confirm the data recorded by Steeno, according to which an enrichment of about 80-90% can be achieved after penetration through the Sephadex Gel filter. In addition to these investigations we also carried out tests with the enriched X-spermatozoa material to determine in vitro penetration through cervical mucus. No decline in the progressive motility of the spermatozoa was observed. After the Gel-filtration sufficient numbers of these were still able to cover penetration distances of 60 mm/hour. The enrichment effect of the X-spermatozoa declined at the beginning of in vitro penetration, but there was no further change in the subsequent course of penetration.

Studies on frequency of Y chromatin in human sperm

The preparation and evaluation of human ejaculate smears on cover glasses enables double-sided examination of the individual sperm heads in the fluorescence microscope. By this method of observation the frequency of Y chromatin in the ejaculates of 19 probands increased significantly to between 1.7 and 6.3%. However, the frequency of 50% Y chromatin-positive sperms theoretically to be expected is not found by applying this technique. Furthermore, sexual abstention of at least 14 days leads to a statistically significant decrease of the frequency of Y chromatin. These observations could explain why the data on Y chromatin frequency reported in the literature appear so inconsistent.

The effects of altering the pH of seminal fluid on the sex ratio of rabbit offspring

It has been suggested that the pH of the vagina at the time of fertilization may have a differential effect on X- or Y-bearing sperm and thereby affect the sex of the offspring. To test this postulate, rabbit semen was collected, diluted 1:10 with a buffer of pH 5.4, 6.9, or 9.6, and after 20 minutes 0.5 ml of semen-buffer mixture was used for insemination in an ovulation-induced female. Newborn pups were examined both externally and internally for gender. The females inseminated with acidic semen had 6 litters, 50 offspring, with 48% males; those with neutral semen had 8 litters, 48 offspring, with 63% males; and those with alkaline semen had 7 litters, 49 offspring, with 49% males. There was no significant difference in these sex ratios from the expected 50% males. Motility of rabbit sperm at 23 degrees C in buffers of pH 4.6, 5.4, 6.9, 9.6, and 9.8 was reduced in vitro as the pH deviated from neutrality. Acid conditions were more detrimental than alkaline conditions. Sperm lost their motility more quickly in buffers of 37 degrees C than in buffers of 23 degrees C. It was not possible with scanning electron microscopy to distinguish morphologically between X- and Y-bearing sperm. It seems unlikely that a direct effect of pH on sperm can be a single influence on the sex of offspring.