Chemical castration

This invention relates to a novel method for the sterilization of male animals and more particularly, relates to a method for chemical castration and chemical contraception of males which is simple, effective and has no undesirable side effects. The method by which chemical castration is accomplished is by injection of an appropriate composition into both spermatic cords or directly into both testes thereby causing atrophy of both testes. A method for chemical contraception without atrophy of testes is accomplished by injecting an appropriate composition into both caudel epididymis. These methods can be used on all kinds of male animals having external testes including domestic animals, farm animals, and exotic or zoo animals. More specifically, the methods comprise injecting aqueous lactic acid into the preferred site.
Many attempts have been made in the past to carry out successfully the sterilization of male animals by chemical means. A variety of chemical agents and mixtures both natural and synthetic have been studied and tested for their ability to render male animals unable to produce off-spring. Also, past efforts to effect such castrations have included various approaches to introducing the selected agents into the male reproductive organs. As examples, certain sclerotic agents have been injected into the caudel epididymis or vas deferens in order to interfere with the passage of live sperm from the testes to the exterior. Tests have also been carried out using various agents for injection into the testes themselves. These methods have been found to have a number of disadvantages such as lack of desired efficacy and/or failure to prevent libido and/or cause uncontrollable necrotic tissue damage.
It has long been possible to castrate male animals by surgical means. Surgical castration involves an open incision, which often results in infections, excessive bleeding, fly infestation and tetanus which can lead to death. Surgical procedures are well known to cause excessive stress in most animals and are never without pain.
The testes of the male animal perform two major functions. One is for spermatogenesis which originates in the seminiferous tubules, and the second is for the production of androgens (testosterone and dihydrotestosterone) which arise from the interstitual cells (Leydig cells). The sperm cells after their production within the testes are liberated into the head of the epididymis and travel to the tail of the epididymis. The tail of the epididymis (caudel epididymis) is made up of a cavernous network of convoluted tubules. The function of the epididymis is for transport, maturation, concentration, and storage of sperm. Upon ejaculation, sperm cells are liberated from the caudel epididymis into the vas deferens and eventually through the penis to the exterior. The function of both spermatic cords is to provide nutrient, gas exchange, and thermo-regulation for the testes by way of the pampiniform plexus vascular system.
It is a unique and essential feature of the invention that the agent be administered into both spermatic cords resulting in complete disruption of the vascular system thus causing testicular atrophy with loss of both spermatogenesis and libido.
Another feature of the invention is to inject lactic acid into both testes resulting in testes atrophy with loss of libido and spermatogenesis or inject into both caudel epididymis resulting in sterilization (contraception) without loss of libido.
The injecting substance which has been found to be most effective is a lactic acid solution. In any event, it is considered most effective to use an aqueous solution. Of particular usefulness is a lactic acid solution which should be U.S.P. grade or better. One such product is a mixture of lactic acid and lactic acid lactate which is equivalent to a total of not less than 85% and more than 90% by weight of lactic acid (U.S.P. grade).
Other materials which can be used for the injection method include acetic acid, acetic anhydride, propionic acid, butyric acid, succinic acid and the like. Lactic acid has been found to be dose related, which is a definite advantage over many other agents.
The chemical castration can be used for feline, canine, equine, bovine, ovine, and procine species of mammals. Specifically, the method is very successful and practical for bulls and male dogs. Injections made into boars, stallions, and male cats are less successful, primarily due to anatomical orientation and proportions of the male genitalia. Among mammalian species which could be successfully treated are those with pendulous type testis, such as male sheep and goats.
Among the limitations on the procedure are size and abnormal genitalia of the male to be chemically castrated. Thus, for more predictable and positive results, the treatment of the bull should be before his weight reaches about 500 pounds. With the dog, treatment of pups is not recommended.
The results of the procedure of the invention is atrophy of the testes by the preferred spermatic cord injections and secondly by intra-testis injections in small bulls causing ultimate loss of both libido and spermatogenesis; thirdly, injections of the caudel epididymis for chemical contraception without loss of libido.
Although it is necessary that veterinarians and others using the invention method have some procedural training, it has been found that a single demonstration or an explanation and/or an insert illustration are entirely adequate.
The invention procedure has been found to provide safe, rapid, economical and practical techniques for castration of animals. More rapid administration of the treatment is possible as compared to surgical castration. All the complications associated with surgical castration procedures are non-existent. Thus, it is safer, more humane, cleaner, and a great deal more convenient in every way than surgical castration.
It is also believed that this procedure of chemical castration may well yield greater performance results, that is for instance, showing increased feed efficiency and rate of weight gain in bulls. Generally, surgical castration has been found to set an animal back in growth at least two weeks. In connection with bulls, it becomes important to understand that chemically castrated bulls are, in reality and every way, steers and not bulls. With respect to bulls weighing in excess of 500 pounds, the situation is no different than for the emasculated or crimped animal. Thus, the larger chemically castrated bulls generally will be found to have non-functional testes remaining as their feeding time is too short to allow the testes to atrophy completely. In bulls weighing less than 500 pounds the animals will probably have no testes and at the time of slaughter, the scrotum will be shrunk.
The method has been shown to be versatile in its application and can be modified for various animals as required. For example, the volume and size of needle, as well as administration placement, can readily be modified for various animal species.
It is further to be noted, and the data obtained on animals has shown this, that lactic acid solution is preferred. It causes few side effects and is consistent in its effects. It is a normal, naturally occurring biological chemical and is therefore safe and predictable. It is, of course, also easy to assay in tissue samples and residues.
More specifically, in testing the chemical castration procedure, concentrations of lactic acid of from 5 to 85% in aqueous solution and from 0.25 to 16 mls. have been tested with success on bulls and male dogs and with limited success in stallions and boars.
The injection site of choice is both spermatic cords. The advantage of this site over intra-testes injections is that one needs only to cause damage to a relatively small area in contrast to the whole testis. However, in small calves (less than 100 lbs) the choice would be the testes injections as the testis is easier to inject and there is not much tissue at this size to destroy. The caudel epididymis injection procedure has the disadvantage of not eliminating libido; however, when a near intact male is desired, this may be the recommended choice such as for those male dog owners wanting a sterile masculine appearing dog and for those cattle owners desiring bulls for heat checking their cows without the risk of getting them bred to an unwanted male.
The invention technique developed for castration of male animals has wide application. This chemical castration has been employed for example, quite satisfactorily with bulls and male dogs. It has been found to be less useful for castration of male cats, pigs and stallions.
With respect to use of the method for bulls, there are approximately fifty to sixty million calves born in the United States each year of which approximately 50% are bull calves; there are potentially twenty to thirty million bull calves, most of which ordinarily undergo castration.
As for dogs, the method of the invention has great usefulness as a safe, rapid and economical method to produce male sterility as an aid in curbing the dog population. There is great need for an economical male sterilizing procedure in animal shelters and in areas where a differential dog license fee scale exists.
The first object of the experimentation was to determine the ease of administration of a chemical agent in several domestic male mammalian species. The use of Giemsa stain and lactic acid was used to determine both physical limitations and area of ensuing damage subsequent to administration. Three possible injection sites were explored, i.e., the spermatic cord, the testis, and the caudel epididymis.
It was found that a sound administrative approach for male dogs was both the caudel epididymis and spermatic cords and for bulls the spermatic cords and testes. It must be noted that caudel epididymis injections were not performed for the bull; however, this site of injection should be easy to administer the chemical agent.
It is very difficult to inject male cats and boars by either the caudel epididymis and spermatic cord approach due to the physical characteristics and orientation of the male genitalia. Administration approaches for rams have not been tested; however, no problems would be anticipated as their genitalia is of the same nature as for the bull.
It has been found that spermatic cord injections in the stallion presented no problem as to ease of administration; however, for reasons unexplainable at this time, the desired efficacy was lacking. Forty-nine injections were made into spermatic cords using various concentrations and volumes of lactic acid. Only nine successes were accomplished and these were not dose dependent.
The invention will be further described and defined by the following Examples, although it is in no way intended to limit the invention thereto.

EXAMPLE 1
A total of 173 bulls ranging in weight from 100 to 635 pounds were studied using both varying concentrations and varying volumes of lactic acid containing agent injected into both spermatic cords. An additional four bulls were emasculated to serve as positive controls. Thirty-seven of the 173 bulls injected weighed in excess of 500 pounds. The results of these studies are shown in Tables I and II below. Qualitatively, it was found that better results are obtained when the invention procedure is used on bulls weighing less than 500 pounds.
It was found that the lactic acid was dose-dependent on body weight. From the results in Tables I and II, it was found that the recommended dosage of 85% lactic acid for various weights is as follows:
______________________________________Minimum Effective Dosage Body Weight Range Percent(ml) (lbs.) Efficacy______________________________________2 200 or less 934 200 to 300 1008 300 to 500 82______________________________________
TABLE I__________________________________________________________________________Individual Bull Efficacy Results Post-Treatment ResultsL.A. Initial Left Side Right Side Blood Serum LevelsTreatment Body Success Success of TestosteroneConc. Vol. Bull Weight Day of (Yes Day of (Yes (mh/ml)(%) (cc) No. (lbs.) Removal or No) Removal or No) Initial Day 13 Final__________________________________________________________________________Controls 1 405 78 Yes 78 Yes -- -- --Emasculated 2 525 110 Yes 110 Yes 2.955 -- 0.047(Crimped) 3 625 110 Yes 110 Yes 0.794 -- 0.222 4 727 110 Yes 110 Yes 1.801 -- 0.0455 1 5 160 13 No 78 No 0.172 0.275 0.381 6 270 13 Yes 78 No 0.383 5.382 4.823 7 290 13 No 78 No 2.645 2.127 2.610 8 335 13 No 78 No 0.284 0.192 3.655 9 395 13 No 78 No 0.290 0.500 5.100 10 400 13 No 78 No 2.709 3.103 4.390 11 425 13 Yes 78 Yes 0.013 0.089 0.063 12 490 13 No 78 No 0.680 1.780 1.773 13 635 13 No 78 No 4.860 1.480 1.37410 1 14 175 13 Yes 78 No 0.524 0.631 0.724 15 205 13 Yes 78 No 0.453 1.045 3.146 16 240 13 No 78 No 4.536 3.560 2.950 17 310 13 Yes 78 No 0.196 0.377 0.368 18 410 13 No 78 No 0.301 0.148 1.525 19 410 13 No 78 No 0.510 3.360 0.672 20 415 13 No 78 No 2.060 0.084 0.748 21 468 13 No 78 No -- -- 7.937 22 525 13 No 78 No -- -- 8.585 23 525 No Testis 78 No 1.350 -- 0.28020 1 24 255 13 Yes 78 No 0.144 0.091 0.935 25 310 13 Yes 78 No 1.720 1.457 2.469 26 400 13 No 78 No 9.340 6.350 0.785 27 418 13 Yes 78 No -- -- 7.927 28 420 13 Yes 78 No 4.418 0.280 2.261 29 420 13 No 78 No 0.370 0.650 5.240 30 460 13 No 78 No 0.380 0.590 0.348 31 485 13 No 78 No 3.550 3.270 2.944 32 506 13 Yes 78 No -- -- 6.01720 2 33 330 13 No 78 No 1.481 3.212 5.179 34 400 13 No 78 No 7.734 1.136 0.540 35 450 13 Yes 78 Yes 2.113 1.748 0.126 36 455 13 No 78 No 1.225 3.433 3.936 37 575 13 Yes 78 No 2.484 8.495 3.10640 1 38 100 84* Yes 84* Yes 0.202 0.070 0.070 39 135 119 No 119 Yes 0.097 0.204 0.204 40 155 112 No 112 Yes 0.525 >6.000 >6.000 41 175 13 Yes 78 Yes 0.013 0.047 0.084 42 180 13 Yes 78 Yes -- -- -- 43 270 13 Yes 78 Yes -- -- -- 44 415 13 Yes 78 Yes 9.597 2.072 0.360 45 435 13 Yes 78 No 3.260 0.050 2.409 46 440 13 Yes 78 No 3.920 0.640 0.360 47 455 13 No 78 No 0.490 0.345 0.776 48 500 13 Yes 78 No -- -- 2.336 49 508 13 Yes 78 No -- -- 5.141 50 525 13 Yes 78 Yes 9.420 0.360 0.321 51 535 13 No 78 No 1.193 0.726 1.247 52 565 13 Yes 78 No 8.070 0.840 0.321 53 600 13 No 78 No -- 9.260 9.04740 2 54 115 46* Yes 46* Yes 0.562 0.085 0.085 55 116 133 Yes 133 Yes 0.072 0.062 0.062 56 143 71* No 71* No 0.040 0.088 0.088 57 150 133 No 133 No 0.314 0.141 0.141 58 150 119 Yes 119 No 0.561 >6.000 >6.000 59 170 133 No 133 No 0.458 0.452 0.452 60 187 133 No 133 No 0.117 0.629 0.629 61 195 119 Yes 119 No 0.442 >6.000 >6.000 62 290 133 No 133 No 0.505 0.994 0.994 63 295 133 Yes 133 No 4.991 0.868 0.868 64 310 133 No 133 Yes 6.702 0.394 2.394 65 335 133 No 133 No 0.370 0.850 0.850 66 415 13 Yes 78 Yes 8.084 0.046 0.108 67 425 110 Yes 110 Yes 0.136 0.112 0.112 68 500 110 No 110 No 6.439 10.707 10.707 69 570 13 Yes 78 No 0.922 7.428 1.219 70 570 13 Yes 78 No 0.292 0.348 0.81540 4 71 351 124 Yes 124 Yes 0.194 0.076 0.076 72 371 124 No 124 Yes 8.348 0.586 0.586 73 401 124 No 124 No 0.256 0.411 0.411 74 447 124 Yes 124 Yes 0.217 0.078 0.078 75 447 18** No 18** Yes 2.241 4.023 4.023 76 463 124 Yes 124 No 0.314 0.765 0.765 77 481 110 No 110 No 2.043 6.663 6.66340 8 78 466 110 No 110 Yes 3.442 1.951 1.951 79 476 124 Yes 124 Yes 0.367 0.111 0.111 80 502 124 Yes 124 No 0.612 0.789 0.789 81 527 124 Yes 124 No 0.829 1.582 1.582 82 595 124 No 124 No 8.961 0.765 0.765 83 596 110 No 110 No 2.150 4.398 4.398__________________________________________________________________________ *= Died from pneumonia **= Died from bloat
TABLE II__________________________________________________________________________Individual Bull Efficacy Results Post-Treatment Results: Initial Final Initial Blood Serum Success Rate Blood SerumVolume of Body Testosterone (Yes or No) Testosterone85% L.A. Bull Weight Level Left Right LevelInjected No. (lbs.) (mg/ml) Day Testis Testis (mg/ml)__________________________________________________________________________1 84 113 0.411 82 Yes Yes 0.051 85 116 0.642 82 No No 1.040 86 129 0.426 82 No Yes 1.535 87 157 0.465 82 No Yes 0.476 88 157 0.439 82 No Yes 2.000+ 89 237 1.670 80 No No 2.000+ 90 255 0.751 80 No No 2.000+ 91 276 2.000+ 80 Yes Yes 0.157 92 303 2.000+ 80 No No 1.626 93 360 2.000+ 80 Yes No 2.000+2 94 132 0.358 82 Yes Yes 0.034 95(a) 139 0.080 73 Yes Yes 0.111 96(b) 148 0.307 90 No Yes 0.648 97 169 0.651 104 Yes Yes 0.038 98 180 0.389 82 Yes Yes 0.066 99 182 0.570 90 Yes Yes 0.044 100 193 1.525 82 Yes Yes 0.056 101 201 0.628 104 No Yes 0.528 102 262 2.000+ 80 No Yes 2.000+ 103 272 2.000+ 80 No No 1.852 104 331 2.000+ 80 No Yes 2.000+ 105 339 2.000+ 82 No No 2.000+ 106 443 5.001 110 Yes No 13.504 107 460 2.888 110 Yes No 0.532 108 483 1.746 110 No No 16.7654 109(a) 146 0.069 60 Yes Yes 0.127 110 170 0.072 104 No Yes 0.182 111 200 0.143 104 Yes Yes 0.136 112 270 2.000+ 87 Yes Yes 0.176 113 273 2.000+ 97 Yes Yes 0.052 114 273 2.000+ 97 Yes Yes 0.062 115 273 0.542 87 Yes Yes 0.062 116 297 2.000+ 86 Yes Yes 0.127 117 305 1.730 100 No Yes 2.000+ 118 328 0.233 99 Yes Yes 0.105 119 384 2.000+ 87 Yes Yes 0.043 120 402 2.000+ 107 Yes No 2.000+ 121 429 0.693 108 No No 0.641 122 433 0.583 99 Yes Yes 0.095 123 438 0.585 107 Yes No 2.000+ 124 441 0.472 107 No Yes 2.000+ 125 445 0.270 99 Yes Yes 0.055 126 445 1.009 86 No No 2.000+ 127 449 1.510 108 No Yes 2.000+ 128 459 0.437 99 Yes Yes 0.075 129 471 0.590 99 Yes Yes 0.093 130 508 1.773 110 No No 1.930 131 510 0.437 110 No No 0.361 132 545 0.310 100 No No 2.410 133 625 0.583 100 Yes No 0.6128 134(a) 140 0.047 21 Yes Yes -- 135 182 0.178 104 Yes Yes 0.120 136 223 0.866 104 Yes Yes 0.115 137 256 2.000+ 56 Yes Yes 0.069 138 281 0.890 56 Yes Yes 0.050 139 290 0.570 56 Yes Yes 0.049 140 291 2.000+ 56 Yes Yes 0.049 141(a) 383 0.203 65 Yes Yes -- 142 399 2.000+ 66 Yes Yes 0.053 143 403 0.680 77 Yes Yes 0.214 144 424 2.000+ 77 Yes Yes >0.040 145 427 0.640 77 Yes Yes 0.198 146(c) 431 0.129 77 No No 2.000+ 147 438 0.363 99 Yes Yes 0.073 148 458 0.414 99 Yes Yes 0.058 149 461 0.983 77 Yes Yes 0.137 150 471 0.347 99 Yes Yes 0.088 151(d) 479 0.825 77 No No 2.000+ 152 504 10.280 110 Yes No 6.469 153 506 0.771 107 No No 2.000+ 154 543 0.418 108 No Yes 0.778 155 561 0.555 100 Yes Yes 0.098 156 563 0.356 100 Yes Yes 0.044 157 573 0.674 108 No No 2.000+ 158 591 2.000+ 107 Yes No 2.000+ 159 600 0.504 110 Yes Yes 0.040 160 618 1.979 108 No No 1.15612 161 255 -- 82 Yes Yes 0.143 162 261 -- 82 Yes Yes 0.056 163 309 2.000+ 86 Yes Yes 0.068 164 393 2.000+ 107 Yes Yes 0.036 165 439 2.000+ 108 Yes Yes 0.149 166 484 1.719 111 Yes Yes 0.154 167 536 0.853 108 Yes Yes 0.180 168 563 0.742 108 No Yes 2.000+ 169 582 0.501 107 No No 2.000+ 170 615 0.678 108 Yes Yes 0.174 171 619 2.000+ 107 Yes Yes 0.17316 172(e) 398 -- 17 Yes Yes -- 173 426 2.277 111 Yes Yes <0.038 174 461 0.716 108 Yes Yes 0.101 175 558 1.109 107 Yes Yes 0.210 176 590 2.000+ 107 Yes Yes 0.202 177 627 2.000+ 108 Yes Yes 0.159__________________________________________________________________________ (a) = Died from pneumonia (b) = Extremely small genitalia to inject (c) = Injected head of right epididymis; approximately 1/2 or right testi destroyed (d) = Injected both heady of epididymis (e) = Removed both testis due to severe ulceration on left side
EXAMPLE 2
Evaluation of High and Low Injection Sites
Twenty bulls had both spermatic cords injected with 8 c.c. of 85% lactic acid to test site of injection in spermatic cords. One side had the injection immediately above the testis and the other side was injected 1 to 11/2 inches above the testis. The results of this study are shown in Table III below. Low injections proved superior to high injections, with an efficacy rate of 95% versus 80%, respectively.
EXAMPLE 3
Effectiveness for Baby Holstein Bulls
One and two c.c. of 85% lactic acid was injected directly into the testis of five small baby Holstein bulls. The experimental design and results are as follows:
______________________________________ Days Old Vol. (c.c.)Bull At Time Injected Efficacy ResultsNo. of Infection Left Right Left Side Right Side______________________________________178 0 1 2 Yes Yes179 33 1 2 No Yes180 7 1 2 Yes Yes181 7 1 2 Yes Yes182 1 1 2 Yes Yes______________________________________
It is evident from this study that lactic acid can be used for very young bulls calves, especially the first week or so following birth.
TABLE III______________________________________EVALUATION OF LOW AND HIGH INJECTION SITESIN TWENTY (20) BULLSTreatment Bull Initial Body Efficacy (Yes or No)Group Number Weight (Pounds) Left Side Right Side______________________________________ LOW HIGH______________________________________A 183 420 Yes Yes 184 375 Yes Yes8 c.c. of 185 460 Yes No85% L.A. 186 335 Yes Yes 187 390 Yes Yes 188 470 Yes Yes 189 405 Yes Yes 190 325 Yes Yes 191 485 Yes Yes 192 370 No No______________________________________ HIGH LOW______________________________________B 193 370 No Yes 194 405 Yes Yes8 c.c. of 195 360 Yes Yes85% L.A. 196 435 Yes Yes 197 390 Yes Yes 198 380 Yes Yes 199 465 Yes Yes 200 375 Yes Yes 201 455 Yes Yes 202 485 No Yes______________________________________
EXAMPLE 4
Evaluation for Canine Sterilization
The use of lactic acid was studied as a possible chemical sterilant in the canine species. The results from injecting lactic acid into the caudel epididymis and spermatic cord are summarized in Tables IV and V, respectively.
The results shown in Table IV clearly demonstrate that 5 to 25% lactic acid functions as an effective chemical sterilant when injected directly into the caudel epididymis. The 85% lactic acid gave severe and prolonged ulceration.
The two control dogs identified as dogs Y and Z receiving surgical ligation of the pampiniform plexus show by comparison that interfering with the pampiniform plexus will sterilize a male dog.
TABLE IV______________________________________SUMMARY OF TISSUE DAMAGERESULTING FROM INJECTINGLACTIC ACID INTO THECAUDEL EPIDIDYMIS OF THE CANINE(Each Line Represents One Injection) Tissue Damage Results % To Scrotal Lactic Volume Gauge Days Post- Caudel Ulcer-Dog Acid Injected .times. Inch Injection Epididy- ationNo. in H.sub.2 O (c.c.) Needle Sacrificed mis (A) (B)______________________________________X Control - Ligated surgically both caudel epididymis; no sperm cells 4 days later1 100 0.25 26 .times. 3/8 9 ++ ++2 25 0.25 26 .times. 3/8 3 ++ 03 20 0.25 26 .times. 3/8 3 ++ 03 20 0.25 26 .times. 3/8 3 ++ 04 20 0.25 26 .times. 3/8 3 + 04 20 0.25 26 .times. 3/8 3 + 05 15 0.25 26 .times. 3/8 3 ++ 05 15 0.25 26 .times. 3/8 3 ?* 06 15 0.25 26 .times. 3/8 3 ++ 06 15 0.25 26 .times. 3/8 3 ++ 07 15 0.25 26 .times. 3/8 3 ++ 07 15 0.25 26 .times. 3/8 3 ++ 08 15 0.25 26 .times. 3/8 7 ++ 08 15 0.25 26 .times. 3/8 7 ++ ++9 15 0.25 26 .times. 3/8 14 ?* 010 10 0.25 26 .times. 3/8 3 ++ 011 10 0.25 26 .times. 3/8 3 ++ 011 10 0.25 26 .times. 3/8 3 ++ 012 10 0.25 26 .times. 3/8 3 ++ 012 10 0.25 26 .times. 3/8 3 + 013 10 0.25 26 .times. 3/8 3 + 013 10 0.25 26 .times. 3/8 3 + 014 10 0.25 26 .times. 3/8 3 0 014 10 0.25 26 .times. 3/8 3 + 015 10 0.25 26 .times. 3/8 7 ++ 015 10 0.25 26 .times. 3/8 7 ++ 016 10 0.25 26 .times. 3/8 7 ++ 016 10 0.25 26 .times. 3/8 7 ++ +17 10 0.25 26 .times. 3/8 7 ++ 017 10 0.25 26 .times. 3/8 7 ++ 018 10 0.25 26 .times. 3/8 14 ++ 018 10 0.25 26 .times. 3/8 14 ++ 019 5 0.25 26 .times. 3/8 3 ?* 020 5 0.25 26 .times. 3/8 3 + 020 5 0.25 26 .times. 3/8 3 ++ 021 5 0.25 26 .times. 3/8 3 ++ 021 5 0.25 26 .times. 3/8 3 ++ 022 5 0.25 26 .times. 3/8 7 + 022 5 0.25 26 .times. 3/8 7 + 023 5 0.25 26 .times. 3/8 14 + 0______________________________________ A 0 = No observable damage + = Partially destroyed ++ = Completely destroyed B 0 = No ulceration + = Small ulceration ++ = Severe ulceration *Difficult to determine influence of epididymis injection vs excess tissu damage resulting from spermatic cord injection
Table V shows the results of injections of 25% to 10% lactic acid. These tests indicate that the percent efficacy for the 25%, 20%, 15%, and 10% lactic acid is 82% (14/17), 100% (6/6), 92% (12/13), and 80% (4/5), respectively.
TABLE V__________________________________________________________________________SUMMARY OF TISSUE DAMAGE RESULTING FROM INJECTING LACTIC ACIDINTO THE PAMPINIFORM PLEXUS OF THE SPERMATIC CORD OF THE CANINE(Each Line Represents One Injection) Tissue Damage Results % Blood To To Lactic Volume Gauge Days Post- Circulation To Head of Testis ScrotalDog Acid Injected .times. Inch Injection To Testis P.P. Epididymis Proper UlcerationNo. in H.sub.2 O (c.c.) Needle Sacrificed (A) (B) (C) (D) (E)__________________________________________________________________________Y Control - Ligated both pampiniform plexus - no sperm cells 7 days laterZ Control - Ligated both pampiniform plexus - no sperm cells 4 days later24 25 0.25 - Injected intra-testis - small area destroyed25 25 0.5 27 .times. 3/4 3 0 0 0 0 025 25 0.5 27 .times. 3/4 3 0 0 0 0 026 25 0.5 26 .times. 3/8 3 +++ ++ ++ ++ 027 25 0.5 26 .times. 3/8 3 0 0 ++ 0 027 25 0.5 26 .times. 3/8 3 0 0 ++ 0 028 25 0.5 26 .times. 3/8 7 +++ ++ ++ 0 028 25 0.5 26 .times. 3/8 7 +++ ++ ++ 0 ++29 25 0.5 26 .times. 3/8 7 +++ ++ ++ ++ 029 25 0.5 26 .times. 3/8 7 +++ ++ ++ ++ 030 25 0.5 26 .times. 3/8 7 ++ + ++ 0 +30 25 0.5 26 .times. 3/8 7 ++ + ++ 0 031 25 0.5 26 .times. 3/8 7 ++ + ++ 0 031 25 0.5 26 .times. 3/8 7 ++ + ++ 0 032 25 0.5 26 .times. 3/8 14 +++ ++ ++ ++ 033 25 0.25 27 .times. 3/4 3 ++ + ++ 0 033 25 0.25 27 .times. 3/4 3 ++ + ++ 0 034 25 0.25 26 .times. 3/8 3 0 0 0 0 034 25 0.25 26 .times. 3/8 3 +++ ++ ++ ++ 035 20 0.5 27 .times. 3/4 3 ++ 0 0 0 035 20 0.5 27 .times. 3/4 3 +++ ++ ++ ++ 036 20 0.5 26 .times. 3/8 3 +++ + + 0 036 20 0.5 26 .times. 3/8 3 +++ + + ++ 037 20 0.25 26 .times. 3/8 3 0 0 ++ 0 037 20 0.25 26 .times. 3/8 3 + + + ++ 0 038 15 1.0 27 .times. 3/4 3 0 0 0 0 038 15 1.0 27 .times. 3/4 3 +++ ++ 0 0 039 15 0.5 27 .times. 3/4 3 +++ 0 0 0 039 15 0.5 27 .times. 3/4 3 +++ 0 0 0 040 15 0.5 26 .times. 3/8 3 +++ ++ + ++ 040 15 0.5 26 .times. 3/8 3 +++ ++ + ++ 041 15 0.5 26 .times. 3/8 3 +++ ++ + ++ 041 15 0.5 26 .times. 3/8 3 + 0 ++ 0 042 15 0.5 26 .times. 3/8 7 +++ ++ ++ ++ 042 15 0.5 26 .times. 3/8 7 +++ ++ ++ ++ 043 15 0.5 26 .times. 3/8 14 + + ++ 0 043 15 0.5 26 .times. 3/8 14 ++ + ++ 0 044 15 0.5 26 .times. 3/8 14 +++ ++ ++ ++ +45 10 0.5 26 .times. 3/8 3 +++ ++ ++ 0 045 10 0.5 26 .times. 3/8 3 +++ ++ ++ + 046 10 0.25 26 .times. 3/8 3 ++ + ++ 0 046 10 0.25 26 .times. 3/8 3 ++ + 0 0 047 10 0.25 26 .times. 3/8 3 0 0 0 0 0__________________________________________________________________________ A 0 = No effect on blood circulation to the testis + = Slight effect on blood circulation ++ = Most of blood circulation is gone +++ = No blood circulation to testis B 0 = No observable tissue damage of pampiniform plexus (P.P.) and spermatic cord area + = Small area destroyed ++ = Severe damage C 0 = No observable damage + = Partially destroyed ++ = Completely destroyed D 0 = No observable damage + = Partial damage ++ = Severe damage; incapable of producing sperm cells E 0 = No ulceration + = Small ulceration ++ = Severe ulceration

Chemical castration

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Pineda et al. Am. J. Vet. Res., vol. 38, No. 6, pp. 831-838, 1977.
Bierschwal et al., Vet. Medicine, 1969, pp. 323-332.
Freeman et al.-Fertility & Sterility, vol. 24, No. 11, pp. 884-890, 1973.
Plant et al.-Australian Veterinary Journal, vol. 55, pp. 263-264, 1979.