Gonadotropins in pituitaries of inbred and linecross beef bulls and effects of irradiation of mammalian pituitary glands on their ability to induce in vitro ovulation of frog ovaries Public Deposited

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  • There were two studies involved in the thesis research. In the first study, variation in the amount of adenohypophysis gonadotropins among 22 individual beef bulls were investigated. These bulls represented four inbred lines, and six linecrosses. The bulls were raised in the Oregon State University purebred herd. The bulls were slaughtered at approximately 1000 pounds live weight. The pituitaries were removed, weighed, individually identified, sealed in glass vials, and frozen at -20°C. until needed for bioassay. Assay material was prepared by dissecting the anterior lobe from the other pituitary material and then crushing the adenohypophysis in a hand operated tissue grinder. Immature male and female mice were used to assay for gonadotropic potency. T-test values showed all bull pituitaries to contain a significant amont of both follicle stimulating hormone and luteinizing hormone when the pituitary-treated mice were compared with control mice. When the Hereford inbred lines of cattle were compared with one another no significant differences were found for gonadotropic potency. However, when the inbred Angus line was compared with each of the inbred Hereford lines, one of the inbred Hereford lines had significantly greater luteinizing hormone activity than the inbred Angus, and another inbred Hereford line had a significantly greater amount of follicle stimulating hormone activity than the inbred Angus. One of the linecrosses had significantly greater luteinizing hormone potency than all four inbred lines, and a different linecross had a significantly greater amount of follicle stimulating hormone potency than three of the four inbred lines. However, one inbred Hereford line had a significantly greater amount of luteinizing hormone than two of the Hereford linecrosses. A comparison of linecrosses showed many significant variations in one or the other gonadotropic potency. It was noted that wherever a significant difference existed, the greater potency for one or the other gonadotropin favored the linecross that had either a sire or dam of inbred Lionheart parentage. In the second study, effects of x-irradiation delivered at rates of 0, 1000, 2000, 3000, 4000, and 5000 r. to excised beef cattle, sheep, and rabbit pituitaries and their subsequent in vitro gonadotropic potency were investigated by use of grass frog ovarian fragments. The pituitary material was added to test tubes at levels of 150, 125, 100, 75, 50, 25, 10, 5, and 1 mg. per test tube. A modified (calcium free) Holtfreter solution was added to each test tube bringing the total volume to 10 ml. in each test tube. A grass frog ovarian fragment was placed in the incubation medium for 48 hours. Following incubation the number of released eggs were recorded. Origin of the ovarian fragments were identified as to ovary and position. Ovulation percentage was affected by the mammalian species from which the pituitaries came, the level of irradiation, and the amount of pituitary added to each culturing test tube. One hundred twenty-five mg. of non-irradiated sheep pituitary was able to induce a very slight amount of frog ovulation. However, sheep pituitary which received 2000 r. induced a much better ovulation percentage with 75 and 100 mg. pituitary material. When the beef cattle pituitary was delivered 1000 r. the ovulation rate remained slight, but ovulation occurred at the 100, 125, and 150 mg. levels. Irradiation levels greater than 2000 r. compared with the 2000 r. level had a depressing effect on ovulation rate. When comparing all rates of irradiation and all levels of rabbit pituitary, 25 mg. of rabbit pituitary which had received 3000 r. appeared best. At this point 40.3 percent ovulation occurred. An analysis of variance was run for all three mammalian species for the radiation rate, the pituitary level, ovary location of the frog, and position of the frog ovarian fragment. The analysis of variance showed that results are not influenced by either of the two ovaries nor by the position of the fragments. The results are significantly affected by the level of pituitary used and the amount of irradiation delivered to the mammalian pituitary.
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