Chemistry: natural resins or derivatives; peptides or proteins; – Peptides of 3 to 100 amino acid residues – 8 to 10 amino acid residues in defined sequence
Reexamination Certificate
2000-04-19
2001-12-04
Davenport, Avis M. (Department: 1653)
Chemistry: natural resins or derivatives; peptides or proteins;
Peptides of 3 to 100 amino acid residues
8 to 10 amino acid residues in defined sequence
C514S012200, C435S069100
Reexamination Certificate
active
06326467
ABSTRACT:
FIELD OF THE INVENTION
The present invention generally relates to methods for sterilizing animals and to methods for medically treating certain sex hormone related diseases such as, for example, cancer of the breast or prostate. More particularly, this invention relates to sterilization and medical treatment by means of chemical attack upon the pituitary gland.
BACKGROUND OF THE INVENTION
Considerable interest exists with respect to the subject of sterilization of animals. This is especially true of those concerned with veterinary medicine and animal husbandry, particularly as they relate to the subject of sterilization of domestic animals such as dogs, cats, cattle, sheep, horses, pigs, and the like. Various methods have been developed over the years to accomplish sterilization. For example, with respect to male cattle, the most widely used procedure for eliminating problems of sexual or aggressive behavior is sterilization through surgical castration. This is done in various ways, e.g., crushing the spermatic cord, retaining the testes in the inguinal ring, or use of a rubber band, placed around the neck of the scrotum, to cause sloughing off of the scrotum and testes. However most of these “mechanical” castration methods have proven to be undesirable in one respect or another; for example they (1) are traumatic, (2) introduce the danger of anesthesia, (3) are apt to produce infection, and (4) require trained personnel. Moreover, all such mechanical castration methods result in complete abolition of the testes and this of course implies complete removal of the anabolic effects of any steroids which are produced by the testes and which act as stimuli to growth and protein deposition.
These drawbacks have caused consideration of various alternative sterilization techniques such as the use of chemical sterilization agents. However, the use of chemical sterilization agents has its own set of advantages and disadvantages. On the positive side, chemical sterilization eliminates the stress and danger associated with mechanical castration. Chemical sterilization also has the added advantage of allowing for retention of certain anabolic effects resulting from a continued presence of low levels of circulating testosterone. This is especially valuable in the case of animals raised for human consumption since circulating testosterone promotes growth, efficiency of feed conversion and protein deposition. Unfortunately, there are several disadvantages associated with chemical sterilization. For example chemical sterilization is often temporary rather than permanent; it also sometimes produces extremely severe, and even fatal, side effects.
Many of these chemical sterilization methods have been aimed at regulation of luteinizing hormone produced at various stages of an animal's sexual development. For example, with respect to cattle it has been established that in the case of the infantile calf, luteinizing hormone is rarely discharged and testicular production of androgens is at low levels. On the other hand, in a prepubertal calf, or an adult bull, discharges of luteinizing hormone from the anterior pituitary occur more frequently and the testes produce considerably larger amounts of testosterone and other steroids. It is thought that these conditions result from the following factors: (1) decreases in the concentration of estradiol receptors in the hypothalamus, (2) concomitant increases in the concentration of estradiol receptors in the anterior pituitary, and (3) increases the number of gonadotropin-releasing hormone (GnRH) receptors in the anterior pituitary. This increase in GnRH receptors is generally regarded as a prerequisite for an animal to pass from the infantile stage to the prepubertal and mature stages of endocrine development. Hence, based upon these understandings of the hypothalamic-pituitary-testicular axis, several chemical methods have been proposed to modify given animals, e.g., a bull calf, in such a way that it never enters puberty, but still receives stimuli for growth and protein deposition through the anabolic effects of steroids produced by modified testes. In any event, most of the chemicals proposed for such sterilization purposes are hormones or hormone analogs. For example U.S. Pat. No. 4,444,759 teaches the use of a class of peptides analogous to GnRH (i.e., gonadotropin-releasing hormone, and particularly luteinizing hormone-releasing hormone) are capable of inhibiting release of gonadotropins by the pituitary gland and thereby inhibiting release of the steroidal hormones, estradiol, progesterone and testosterone. It should also be noted that the terms “GnRH” (gonadotropin-releasing hormone) and “LHRH” (luteinizing hormone-releasing hormone) are sometimes used interchangeably in the literature. For the purposes of describing the prior art both terms may be employed; however, for the purposes conveying the teachings of our patent disclosure, applicants prefer the term GnRH and will use it in describing their compounds.
Be that as it may, some prior art chemical sterilization procedures are specifically adopted to alter luteinizing hormone secretion before the animal has attained the age of puberty. This is not surprising since the role of luteinizing hormone in sexual maturation is well known. Luteinizing hormone is a gonadotropic hormone found in the anterior lobe of the pituitary gland and, in male animals, it is known to stimulate the interstitial cells of the testes to secrete testosterone (see generally, The Merck Index, 8th edition, p. 560 (1968), Encyclopedia of Chemical Technology, Vol. 7, pp. 487-488 (1951)).
One approach has been to use certain chemicals to produce antibodies in an animal which exhibit cross-reactivity with the gonadotropins produced by the animal's pituitary gland. It is generally thought that with such early antigenic stimulation, formation of antibodies is more continuously stimulated by the release of endogenous hormones and that early immunization with such luteinizing hormone deters the maturation of the gonads and adnexal glands. This, in turn, is thought to inhibit spermatogenesis at the spermatogonial level. For example, U.S. Pat. No. 4,691,006 teaches injection of a compound having an amino acid sequence of at least 20 units for purposes of eliciting formation of antibodies which exhibit cross-reactivity with the gonadotropins produced by the animal's pituitary. With early antigenic stimulation of this kind, the formation of such antibodies is more continuously stimulated by release of endogenous hormones. Early immunization with such luteinizing hormone also deters the maturation of the gonads and adnexal glands. However, the art has also recognized that early immunization of this kind may tend to make the interstitial tissues fibroblastic. It has also been found that such early stimulation of the immunologic system leads to development of a high titered antiserum to luteinizing hormone which remains at relatively high levels. Nonetheless, periodic boosters of such compounds are often necessary even for adult animals sterilized before puberty in order to maintain high levels of the neutralizing antibodies.
Similarly, luteinizing hormone has been administered to animals after they have attained the age of puberty in order to atrophy their reproductive organs and to cause a decrease in libido (see generally, M. Tallau and K. A. Laurence, Fertility and Sterility, Vol. 22, No. 2, February 1971, pp. 113-118, M. H. Pineda, D. C. Lueker, L. C. Faulkner and M. L. Hopwood, Proceedings of the Society for Experimental Biology and Medicine, Vol. 125, No. 3, July 1967, pp. 665-668, and S. K. Quadri, L. H. Harbers, and H. G. Spies, Proc. Soc. Exp. Biol. Med., Vol. 123, pp. 809-814 (1966). Such treatments also impair spermatogenesis in noncastrated adult male animals by interruption of the spermatogenic cycle.
Other chemical sterilization agents have been specifically designed for use on female animals. For example, it is well known that certain antigens will produce an antiserum against a requisite estrogen. This is
Glode Leonard Michael
Jarosz Paul J.
Nett Torrance M.
Wieczorek Maciej
Colorado State University Research Foundation
Davenport Avis M.
Sheridan & Ross P.C.
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