title: Effect of storage temperature on sperm cryopreservation.
abstract: OBJECTIVE
  To evaluate the influence of cryopreservation temperature on human sperm motility and morphology.
  
  
  METHODS
  Controlled study, investigator was blinded to the type of cryopreservation.
  
  
  METHODS
  University-based andrology laboratory.
  
  
  METHODS
  Sixteen semen samples with normal motility and sperm count from men after a fertility work up.
  
  
  METHODS
  Semen aliquots were either stored in a mechanical freezer at -70 degrees C or in liquid nitrogen at -196 degrees C for 7 days or 3 months. Test yolk buffer was used as a cryoprotectant. With use of a programmable freezing unit, all samples were cooled at a controlled rate.
  
  
  METHODS
  Sperm motility and morphology.
  
  
  RESULTS
  After 7 days of cryopreservation, there was a greater decrease in sperm motility among specimens maintained at -70 degrees C than among those maintained at -196 degrees C (47% versus 39% decrease). The difference in sperm motility was even greater after 3 months of cryopreservation (72% versus 39% decrease). No difference in postthaw sperm morphology was detected among sperm preserved at -70 degrees C versus -196 degrees C.
  
  
  CONCLUSIONS
  Sperm cryopreservation at -196 degrees C is superior to cryopreservation at -70 degrees C. Sperm can be stored at -70 degrees C for a short period of time with a relatively modest loss of motility.
authors.affiliation: Division of Urology, University of Colorado Health Science Center, Denver, USA. harald.trummer@kfunigraz.ac.at
authors.forename: H
authors.initials: H
authors.lastname: Trummer
authors.forename: K
authors.initials: K
authors.lastname: Tucker
authors.forename: C
authors.initials: C
authors.lastname: Young
authors.forename: N
authors.initials: N
authors.lastname: Kaula
authors.forename: R B
authors.initials: RB
authors.lastname: Meacham
mesh_terms: D015925:Cryopreservation; D006801:Humans; D008297:Male; D013048:Specimen Handling / Q000379:methods*; D013081:Sperm Motility / Q000502:physiology*; D013696:Temperature