Conventional techniques Several methods have been used to sort<unk>  before the advent of flow cytometry. Density gradient centrifugation (in a continuous or discontinuous gradient) can concentrate semen samples with low concentration of<unk> , using the density of<unk>  as a measure of their quality. Similarly, so-called swim-up techniques apply a centrifugation step and then<unk>  is allowed to swim up into a medium, thus enriching a subpopulation of motile<unk> . However, use of<unk>  centrifugation is detrimental to the<unk>  viability and elicits production of reactive oxygen species. Conventional techniques are routinely used in assisted reproductive technology. Flow cytometry Flow cytometry is another method used to sort<unk>  and adaptations of this technique opens new opportunities in<unk> . However, because flow cytometry-based<unk>  often uses fluorescent dyes that often stain DNA, the safety of this technique in human reproductive medicine is a matter of scientific discussion. However, flow cytometry is the only currently used technique able to determine the sex of future progeny by measuring DNA content of individual<unk>  cells. It evaluates if they contain the larger X chromosome (giving rise to a female offspring) or smaller Y chromosome (leading to male progeny). It then allows separation of X and Y<unk> . The so-called Beltsfield<unk>  Sexing Technology was developed by USDA in conjunction with Lawrence Livermore National Laboratories, relying on the DNA difference between the X- and Y- chromosomes. Prior to flow cytometric<unk> , semen is labeled with a fluorescent dye called Hoechst 33342 which binds to the DNA of each<unk> atozoon. As the X chromosome is larger (i.e. has more DNA) than the Y chromosome, the "female" (X-chromosome bearing)<unk> atozoa will absorb a greater amount of dye than its male (Y-chromosome bearing) counterpart. As a consequence, when exposed to UV light during flow cytometry, X<unk> atozoa fluoresce brighter than Y-<unk> atozoa. As the<unk> atozoa pass through the flow cytometer in single file, each<unk> atozoon is encased by a single droplet of fluid and assigned an electric charge corresponding to its chromosome status (e.g. X-positive charge, Y-negative charge). The stream of X- and Y- droplets is then separated by means of electrostatic deflection and collected into separate collection tubes for subsequent processing. Another cytometric technique used in<unk>  is magnetic-activated cell<unk>  (MACS) which is routinely applied in assisted reproduction hospitals to sort out<unk>  with fragmented DNA. This is achieved using antibodies to surface markers of programmed cell death (apoptosis) such as annexin V, coupled with magnetic beads. Following the binding of these antibodies,<unk> atozoa which undergo apoptosis are sorted by applying magnetic field to the<unk>  suspension. MACS obviates the need for fluorescent DNA binding molecules. Other techniques DNA damage in<unk>  cells may be detected by using Raman spectroscopy. It is not specific enough to detect individual traits, however. The<unk>  cells having least DNA damage may subsequently be injected into the egg cell by intracytoplasmic<unk>  injection (ICSI). Many other methods for<unk>  have been proposed or are currently tested. To select<unk> atozoa with low DNA damage index the population of<unk>  could be enriched with<unk> atozoa with non-fragmented DNA, with techniques like electrophoresis, Z method and MACS (Magnetic Activating Cell<unk> , which in combination with density gradient centrifugation in single<unk>  preparation protocols results in<unk> atozoa with superior quality. Hyaluronic acid (HA) binding sites on the<unk>  plasma membrane are an indicator of<unk>  maturity (Huszar et al., 2003, Yudin et al.,1999). There are two methods based on this fact: physiological intracytoplasmic<unk>  injection (PICSI), and a<unk>  slow procedure; both methods require<unk>  preparation via<unk>  washing or centrifugation.
Sperm sorting
Postcoital test
Fertility testing
Cytogenetics
Semen collection
Karyotype
Triple smear
Magnetogenetics