Endocrine regulation of final oocyte maturation and sex differentiation in salmonids Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/pz50h030f

Descriptions

Attribute NameValues
Creator
Abstract or Summary
  • Sexual maturation and sex differentiation comprise facets of a common theme: reproduction. The endocrine system regulates many of the critical physiological processes necessary for reproduction and offers a framework within which technologies can be developed for controlling sexual maturation and sex differentiation. The studies described in this thesis were undertaken to improve the understanding of the endocrine control of these critical stages of development in salmonids. Final ovarian maturation in salmon is accompanied by dynamic changes in plasma hormone levels. Ovulation can be accelerated through the use of hormones such as gonadotropin releasing hormone or its analogs (GnRHa). The effectiveness of GnRHa often depends on the timing of treatment. To determine if plasma concentrations of steroids can be used to predict the sensitivity of adult female coho salmon (Oncorhynchus kisutch) to GnRHa, circulating levels of testosterone, 17α,20β-dihydroxyprogesterone (DHP), and estradiol were measured before and after injection with GnRHa to accelerate ovulation. We found that high levels of testosterone were predictive of early response of coho salmon to GnRHa treatment. The correlation between testosterone and ovulatory response to GnRHa suggested a possible functional relation. However. implantation or injection of testosterone. 17α-methyltestosterone (MT), or the antiandrogen, cyproterone acetate (CA), before or with GnRHa treatment did not affect the ovulatory response of coho or chinook salmon ( 0. tshawytscha) to GnRHa. Chinook salmon treated with MT alone had accelerated ovulation in comparison to controls. If steroids are involved in sex differentiation. steroids must be produced early in development. In vitro production of steroids in both coho salmon and rainbow trout (0. mykiss) was assessed from hatch through sex differentiation. Cortisol, androstenedione, testosterone, and estradiol were produced just after hatching by tissue explants that contained anterior kidneys and gonads of coho salmon. To circumvent the problem of not knowing the sex of individuals until after sex differentiation, single-sex populations of rainbow trout were produced by gynogenesis or androgenesis. Tissue explants produced more androstenedione than testosterone or estradiol. More androgens were produced by testes and more estradiol was produced by ovaries within 6 to 10 weeks of hatching. Dietary treatment with estradiol or MT inhibited gonadal steroid secretion. Electrophoresis of gonadal homogenates from salmonids revealed several sex-specific bands. In particular, a prominent band of about 50,000 daltons was apparent in ovaries but not testes. Production of sex-specific proteins may be affected by dietary steroid treatment.
Resource Type
Date Available
Date Copyright
Date Issued
Degree Level
Degree Name
Degree Field
Degree Grantor
Commencement Year
Advisor
Academic Affiliation
Non-Academic Affiliation
Subject
Rights Statement
Peer Reviewed
Language
Digitization Specifications
  • File scanned at 300 ppi (Monochrome, 256 Grayscale) using Capture Perfect 3.0 on a Canon DR-9050C in PDF format. CVista PdfCompressor 4.0 was used for pdf compression and textual OCR.
Replaces
Additional Information
  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2013-02-21T17:42:06Z (GMT) No. of bitstreams: 1 FitzpatrickMartinStone1991.pdf: 8512589 bytes, checksum: 115ff9808d01ff98acab5fb7cf985e08 (MD5)
  • description.provenance : Submitted by Kirsten Clark (kcscannerosu@gmail.com) on 2013-02-20T22:55:48Z No. of bitstreams: 1 FitzpatrickMartinStone1991.pdf: 8512589 bytes, checksum: 115ff9808d01ff98acab5fb7cf985e08 (MD5)
  • description.provenance : Made available in DSpace on 2013-02-22T17:02:17Z (GMT). No. of bitstreams: 1 FitzpatrickMartinStone1991.pdf: 8512589 bytes, checksum: 115ff9808d01ff98acab5fb7cf985e08 (MD5) Previous issue date: 1990-05-29
  • description.provenance : Approved for entry into archive by Patricia Black(patricia.black@oregonstate.edu) on 2013-02-22T17:02:17Z (GMT) No. of bitstreams: 1 FitzpatrickMartinStone1991.pdf: 8512589 bytes, checksum: 115ff9808d01ff98acab5fb7cf985e08 (MD5)

Relationships

Parents:

This work has no parents.

Last modified

Downloadable Content

Download PDF

Items