Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Capsules
Reexamination Certificate
2000-08-23
2003-07-22
Naff, David M. (Department: 1651)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Capsules
C424S489000, C424S093700, C424S561000, C424S811000, C435S002000, C435S178000, C435S182000
Reexamination Certificate
active
06596310
ABSTRACT:
BACKGROUND OF THE INVENTION
CROSS REFERENCE TO RELATED APPLICATION
None.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT
None.
(1) Field of the Invention
The present invention relates to an artificial insemination method which comprises providing sperm in a particle wherein the particle provides for the timed release of the sperm. In particular, a method for artificial insemination wherein the sperm in the particle is naturally or artificially capacitated after the artificial insemination. The present invention further relates to a method for encapsulating the sperm in particles and to the particles comprising sperm. In particular, the present invention relates to methods and particles wherein the sperm is provided in a semen extender that provides an energy source which does not facilitate capacitation of the sperm while in the particle. In a preferred embodiment, the particle comprising the sperm is a capsule or a bead.
(2) Description of Related Art
There is increasing demand for genetic transfer and using stored semen for artificial insemination as a means for genetically selecting animals with desirable traits such as production efficiency and meat quality. This demand has prompted a search for methods of storing semen that abrogates the decrease in viability of semen which occurs under prolonged storage. For example, the fertilizing ability of boar semen decreases during storage. Fertility of boar semen stored in liquid at 64° F. in presently available extenders decreases from day one and is substantially diminished after 5 to 7 days. Thus, the farrowing percentages of sows inseminated artificially with semen after 5 days in storage are about half of the farrowing percentages of sows inseminated on the day of semen collection. The limited shelf life of boar semen not only restricts the shipping of semen samples to distant farms but also demands frequent deliveries, thus, the cost of artificial insemination is increased.
Another inherent problem of artificial insemination is the lack of a reliable method for determining the time of ovulation. Heat (standing estrus) detection allows the stockman to estimate when ovulation may occur. Females may be sexually receptive for 1-3 days, depending upon their age and previous experience. The natural estrous cycle in swine varies from individual to individual and ranges from 17 to 25 days. In addition, some sows may ovulate 12 to 24 hours before standing estrus; others may not ovulate until after estrus is detected. This inconsistent timing of ovulation in relation to standing heat further adds to the difficulties in determining when a sow should be inseminated. It is currently recommended that females be inseminated two or three times to compensate for inaccurate heat detection and variations in the timing of ovulation in relation to heat detection.
Currently, the most common method for storing semen is cryopreservation. However, thawing semen that has been frozen generally results in sperm damage.
Furthermore, cryopreservation also causes premature capacitation, which has been proven in bovine spermatozoa, thus, decreasing fertilization ability of the sperm (Cormier et al. J. Androl. 18: 461-468 (1997)). Therefore, there have been attempts to find other means for storing semen or for more effectively cryoprotecting the sperm.
Encapsulation of cells involving the polymerization of polyelectrolytes by multivalent ions is one of the most common methods for immobilizing whole cells. The first example of immobilizing a whole cell by this method was reported by Hackel et al. (Eur. J. Appl. Microbiol. 1: 291-293 (1975)). Currently, whole cell immobilization often uses ionically cross-linked alginate because it is considered non-toxic, economical, and simple to perform. Furthermore, alginate capsules can be coated with polylysine to increase the mechanical stability of the capsules.
U.S. Pat. No. 5,744,337 to Price et al. teaches using alginate to produce microspheres of controllable size in a method that involves internally controlling gelation of alginate in an oil:water emulsion. The method has been used to produce microspheres containing whole cells. The method allows the production of uniform spherical capsules less than 1,000 microns in diameter.
U.S. Pat. No. 5,912,005 to Lanza et al. teaches a method for implanting cells in a host using cells encapsulated in a temperature independent gel. The method uses ionically cross-linked alginate as the encapsulating material; however, to avoid having to use immunosuppressive chemicals to prevent host immune responses to the implanted capsules, the capsules are not coated with polylysine.
U.S. Pat. No. 5,846,530 to Soon-Shiong et al. teaches a method for encapsulating cells for transplantation wherein to strengthen the capsule, the polymer is covalently cross-linked. The covalently cross-linked capsules remain intact in the host for a longer period of time than tonically cross-linked capsules. The patent teaches covalently cross-linking lipids, polysaccharides such as alginate, and polycations to form capsules containing cells.
U.S. Pat. No. 5,084,350 to Chang et al. teaches a method for encapsulating cells consisting of encapsulating the cells in an ionically cross-linked alginate capsule, suspending the capsules in a solution and forming droplets containing one or more capsules, gelling the droplets, forming membranes on the droplets consisting of tonically cross-linked polylysine, and then liquefying the internal alginate capsules. The end product is a cross-linked polylysine capsule containing cells. The method prevents production of capsules containing cells that are trapped within the membrane.
U.S. Pat. No. 5,451,411 to Gumbotz et al. teaches using alginate capsules containing selected polyanions such as polyacrylic acid to shield the therapeutic agent therein from interaction with the alginate. For use in the host, the capsules are treated prior to use with an acid to reduce the molecular weight of the alginate and to prevent its interaction with the therapeutic agent.
Alginate has been used to encapsulate sperm cells. For example, Esbenshade and Nebel (Theriogenology, 33: 499-508 (1990)) encapsulated boar semen in capsules consisting of alginate capsules coated with polylysine. However, they found that the encapsulation caused an accelerated decrease in motility of the boar sperm. There was a complete loss of motility by 16 hours after encapsulation. The fertilizibility of the sperm was not evaluated. In another example, Nebel et al. (J. Anim. Sci. 60: 1631-1639 (1985)) encapsulated bovine sperm in polylysine coated alginate capsules; however, the sperm showed diminished motility and complete loss of fertility after encapsulation. In an effort to reduce spermatozoal injury of encapsulated sperm, Nebel et al. (Reprod. Fertil. Dev. 5: 701-712 (1993)) encapsulated sperm in polymers consisting of polylysine, polyvinylamine or protamine sulfate. The encapsulated sperm was capable of fertilization, but the encapsulated sperm were at a disadvantage to non-encapsulated sperm when cows were inseminated at conventional times.
Another approach to encapsulating sperm was the use of a thermal gel, wherein the thermal gel was solid at room temperature and liquid at body temperature. U.S. Pat. No. RE34,326 to van Blerkom teaches a method for encapsulating sperm for artificial insemination in nontoxic polymers such as polyurethane-polyether polymers which are freely flowing at body temperature and a gel or solid at room temperature. Bovine sperm encapsulated in the polymer and stored for 14 days at 7° C. retained about 48% of its motility. Fertility of the sperm was not determined.
Therefore, while the prior art has taught methods for encapsulating semen, the prior art has not provided a proven means for prolonging the shelf life of liquid semen or reducing the damage to frozen semen. Thus, there remains a need to prolong the shelf life of semen, particularly the shelf life of boar semen. There is also a need for a method to extend the fertile period of the sperm cells in the femal
Chou Kuo-Chuan Karen
Wang Henry Y.
Board of Trustees operating Michigan State University
McLeod Ian C.
Naff David M.
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