title: Interferometry in flow to sort unstained X- and Y-chromosome-bearing bull spermatozoa.
abstract: BACKGROUND
  It was found earlier that the difference in volume between unstained X- and Y-chromosome-bearing sperm heads could be detected using interference microscopy in visible light. This could be the basis for an alternative to the conventional method to sort X and Y sperm, which uses DNA staining and ultraviolet (UV)-excitation that may be harmful to sperm cells. A novel technique is introduced combining interferometry with flow cytometry.
  
  
  METHODS
  Interference optics were built into an existing flow cytometer/cell sorter and used to sort fresh unstained bull sperm cells on the basis of their head volume. Sorted fractions were stained with a DNA stain, and reanalyzed using the conventional method.
  
  
  RESULTS
  Purities between 60-66% were found in both X- and Y-enriched fractions. It was possible to sort up to 300 cells per second. The system was found to be less sensitive to the orientation of sperm cells than the conventional method.
  
  
  CONCLUSIONS
  Interferometry can be combined with flow cytometry and used to obtain significantly enriched fractions of X- and Y-bearing sperm without staining and UV light. Sorting speeds and purities at this point, however, are much lower than with the conventional method.
authors.affiliation: Holland Genetics, Arnhem, The Netherlands. munster@science.uva.nl
authors.forename: Erik B
authors.initials: EB
authors.lastname: van Munster
mesh_terms: D000818:Animals; D002417:Cattle; D048429:Cell Size / Q000235:genetics; D004247:DNA / Q000032:analysis; D005434:Flow Cytometry / Q000295:instrumentation / Q000379:methods*; D007368:Interferometry / Q000295:instrumentation / Q000379:methods*; D008297:Male; D010775:Photic Stimulation / Q000295:instrumentation / Q000379:methods; D015203:Reproducibility of Results; D013094:Spermatozoa / Q000166:cytology* / Q000378:metabolism; D014960:X Chromosome / Q000235:genetics*; D014998:Y Chromosome / Q000235:genetics*
chemical_list: D004247:DNA