(1) washing:
following centrifugation, resuspension of the sperm pellet into
an inert buffered media. This technique does not eliminate dead
sperm or debris from the resuspended washed sperm
(2) swimup:
following centrifugation an inert buffered media is layered over
the unagitated sperm pellet and some of the motile sperm will
swim toward the surface. This technique generally takes 30-60
minutes for the sperm to swim out of the pellet, and then the
media near the surface with the motile sperm is collected. There
will be a lower sperm count following this procedure due to the
elimination of dead sperm but the quality of the motile sperm
may be improved
(3) gradient differential centrifugation:
inert particles are suspended in an inert buffered media at differing
densities (concentrations) and layered so that following centrifugation
the motile sperm fraction of the semen will be found isolated
within a certain layer (density). Percoll (silicone particles
with polyvinyl pyrrolidine links) was widely used for this indication
until removed from this market in 1996 when potentially hazardous
endotoxin levels were identified. Research has suggested that
the recovery of motile sperm is better with Percoll than with
the swimup technique, and that the harmful effects of oxygen reactive
species of molecules is less significant with the Percoll technique
as compared to swimup. Other particles are now available for differential
centrifugation, one of the most common in 1997 being "Isolate."
(4) others:
swimup into chemicals such as hyaluronidase or filtration through
glass wool (which reportedly will adhere selectively to dead sperm)
are occasionally used but not widely accepted at this time.
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