Classifying – separating – and assorting solids – Sifting – Special applications
Reexamination Certificate
2000-10-10
2002-03-19
Walsh, Donald P. (Department: 3641)
Classifying, separating, and assorting solids
Sifting
Special applications
C209S017000, C209S248000, C209S250000, C209S255000, C209S257000
Reexamination Certificate
active
06357596
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention is a method and apparatus that provides an inexpensive, quick, and portable means to separate motile sperm from a sperm sample. The invention passively filters the motile sperm using a nucleopore membrane.
2. Background Art
Artificial insemination has become a much more frequent procedure due to a variety of sociological, economic, and perhaps environmental reasons. The number of inseminations in the United States and worldwide has been increasing, and will likely continue to increase. A number of causes have been cited for this increase. The age of childbearing has increased, as people are delaying children and marriage. The increased age lowers the probability of fertilization for both men and women. More and more women are also raising children by themselves without a partner, and electing artificial insemination as a means of fertilization. In addition, those that would otherwise not be able to have children now have a medical option that is relatively affordable. An additional factor may be that the sperm count among males has been declining, making fertilization more difficult. And finally, environmental factors have been blamed for decreased fertility of both men and woman.
There are currently a wide array of artificial insemination methods such as, intracervical, intrauterine (IUI), intratubular and direct intraperitoneal (DIPI) insemination, gamete intrafallopian transfer (GIFT), in vitro fertilization and embryo transfer (IVFET), zygote intrafallopian transfer (such as ZIFT, PROST and TET), peritoneal oocyte and sperm transfer (POST), and sex selection, among others. As technology advances, other methods are certain to follow, however, regardless of the process, high motile sperm are preferred. And, most of the facilities that perform the insemination do not have the resources to separate motile sperm, requiring a separate visit to a facility that possess the separation means.
As an example, the Intrauterine Insemination (IUI) and In Vitro fertilization (IVF) methods attempt to recreate the reproductive process by placing sperm and eggs together in an environment conducive to fertilization, either in the womb or outside the womb. The fertilization process requires the sperm to actively invade the egg and commence fertilization. Motile sperm are much more likely to penetrate the egg.
A typical semen sample contains materials such as paternal plasma, protein, leukocytes, spermdecapitation factors and other extraneous materials, and dead, agglutinated or nonviable spermatozoa. These materials are known to interfere with successful fertilization, and with the successful maintenance of a fertilized ovum in the female patient. As an example, seminal plasma can cause severe uterine cramping, and in a worst case results in spontaneous abortion of the fertilized ovum. Thus, it is desirable to remove those spermatozoa having relatively low motility or possessing unhealthy, damaged or abnormal membranes.
The total number of sperm in an ejaculate is a measure of fertility, however, the percentage of motile sperm is more important, especially when considering alternate reproductive means.
Sperm are categorized according to the their exhibited motility, as exhibited by Table 1.
TABLE 1
Motility Index
Degree of Motility
Type of Motility
0
No motility, or movement of tail with no
forward progression
1
20% or less showing forward progression
(sluggish movement)
2
20%-50% showing forward progression
3
50%-80% showing forward progression
4
80%-100% showing forward progression
(very rapid movement)
The percentage of motile sperm showing progressive swimming movements is a measure of the fertility of the sperm sample. The higher the percentage, the higher quality of the sperm sample, and the greater the likelihood that the sample will achieve fertilization.
A high quality sperm sample is important for many reasons. The process of artificial insemination is not only costly economically, but is psychologically expensive. Unsuccessful attempts have devastating effects on the patients.
Higher quality sperm samples are also important considerations when the sample is subject to freezing or aqueous dilution, because these processes tend to kill or weaken the sample. Thus, only the highest quality sperm may survive the processing procedures to which the sperm are subjected.
In summary, higher viability spermatozoa are more likely to lead to successful fertilization and impregnation. The higher quality sperm are also more likely to survive freezing (cryopreservation) and other processing procedures.
In order to reduce the aforementioned problems, attempts have been made to provide a simple, portable, and inexpensive method and device for the filtration of sperm. However, the prior art devices and methods had significant disadvantages and shortcomings.
Various methods of selecting the more active sperm have been utilized in the past, such as the swim up, swim down and Percoll density gradient centrifugation techniques. Swim-up methods are commonly used to process fresh or frozen specimens for the IUI and IVF procedures. The sperm is placed in a medium and subjected to a centrifuge process. The more motile sperm swim to a level where they can be extracted. Such methods employ multiple tube and centrifugation steps that are time consuming and can lead to a low recovery of motile sperm.
TABLE 2
Characteristics of Prior Art Methods
Enhance-
Feature
Swim-Up
Strain Ex
Percoll
S Plus
Sperm
None
None
1
1 wash/
Preparation after
wash/
centri-
liquefaction
centrifugation
fugation
Preparation of
Prepare
None
Build a
Build a
device
buffer
2 step
2 step
solution,
gradient
gradient
pour
into
plate
Sperm Quality
Swim-Up
Strain-Ex
Percol
Enhance-
S Plus
Motility
Higher %
Higher %
Same motility
Same
motile
motile
motility
Viability
unknown
unknown
unknown
unknown
Leukocyte
unknown
unknown
unknown
unknown
contaminants
Washes required
None
None
1-2
1-2
after separation
Total #
1
1
2-3
2-3
Centrifugation
Endotoxin
No
No
Yes
Yes
Contamination
One prior art device used for separating motile sperm from a sperm sample is the migration-sedimentation chamber. This system uses a culture medium with the sperm sample suspended in a medium, and requires a centrifuge to rapidly spin the chamber to separate motile sperm. And, because it is an active process, it increases the likelihood that motile sperm will be excluded from the sample set or damaged during the process, producing a lower recovery sample.
In operation, the sperm sample is placed in a migration-sedimentation chamber, preferably in the lower well portion. The chamber is subjected to centrifugation, and the re-suspended sperm pellet is transferred to the gallery segment of the chamber. The portion of sperm in the well is the motile portion, and is used for insemination.
U.S. Pat. No. 5,185,246 ('246) is a method for semen analysis employing a membrane separation. This patent discloses a method to separate the particulate (cells, spermatozoa, and other particulate) in the whole semen from the seminal plasma which contains many soluble compounds, proteins, hormones, small molecules and electrolytes. The pore size is specifically designed for such a separation, and all sperm cells are blocked from passing through the membrane. The driving force of the '246 patent is a vacuum, and the sperm cells are stuck to the filter, dead and immobile, amenable only for in-situ testing or further disruption. A specific volume, preferably 100 microliters with various aqueous dilutions is employed. The separation apparatus of the '246 patent is a well filter plate that is used for multiple testing in the same round of processing.
The '246 patent is related to tests of andrological significance that need be performed on either the seminal plasma (in the absence of sperm cells) or on the surface of the sperm cells (in the absence of the seminal plasma). But, the cells in these cases need not be viable, need not be motile, and need not be freely dispersed in an aqueous buffered medium fo
Bar-Ami Shalom
Rivnay Benjamin
Stroh Helene
Weichselbaum Amnon
Asmus Scott J.
Maine Vernon C.
Miller Jonathan R
Seibel Machelle
Walsh Donald P.
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