Document Type

Thesis - Open Access

Award Date

1988

Degree Name

Master of Science (MS)

Department / School

Biology

First Advisor

Nels H. Granholm

Abstract

This research concentrated on the reproductive problem associated with the Ay. Granholm and Breck reported that lethal yellow females never produced more than three litters when put into production at puberty. Ay/a females are as reproductively efficient as their a/a littermates at a young age. Ay/a females progressively become obese and reproductively senescent beyond the age of 120 days. The obese Ay/a females beyond 120 days exhibit lower uterine weights and depressed ovulation. Upon treatment with exogenous pituitary gonadotropins, follicle stimulating hormone (FSH) and luteinizing hormone (IH), the reproductively senescent AY/S! females' ovulatory rates were restored to near control levels. In mammalian reproduction the olfactory system provides for effective communication within some species. A pheromone in the urine of the male causes the medial basal region of the hypothalamus of the female mouse to secrete a neurohormone known as gonadotropin releasing hormone (GnRH). GnRH acts on the anterior pituitary gland stimulating the synthesis and release of two gonadotropins, follicle stimulating hormone (FSH) and luteinizing hormone (IH). FSH and IH along with prolactin, which is also secreted by the anterior pituitary gland, regulate the cellular and endocrine functions of the ovary. The hypothalamus stimulates the production of prolactin by the pituitary differently than the gonadootropins. The hypothalamus produces dopamine, a catecholamine, which depresses the production of prolactin. When the dopamine is reduced, the prolactin production increases; thus this is known as prolactin inhibitory factor (PIF). Dopamine is a neurotransmitter that is found in several parts of the brain, especially in the midbrain, where it travels to receptors on the lactotrophs in the anterior pituitary which regulate prolactin synthesis and release. High plasma prolactin concentrations have been seen to increase dopamine turnover in the median eminence followed by depressed prolactin secretion. As previously mentioned FSH, LH and prolactin regulate the cellular and endocrine functions of the ovary. IH stimulates the stromal cells of the adult ovary to produce and release steroids, and androgens, estrogens, and progestins, from the ovary. Growth and maturation of the follicles depends upon FSH; the number of mature Graafian follicles is positively correlated to the concentration of plasma FSH. The two major steroids, estrogen am progestagen, reflect the cyclicity of ovarian activity. Prior to ovulation estrogen is the dominant steroid am following ovulation progestagen is the dominant steroid. This cycle is called the estrous cycle. The need for this cyclicity is due to the two distinct functions of the female reproductive tract. It must act to transport gametes to the site of fertilization. This is the estrogen dominated cycle. Also it provides a site of implantation of the fertilized egg am supplies nutrients to the embryo. This is done in the progestogenic part of the cycle.

Library of Congress Subject Headings

Mice as laboratory animals

Mice -- Reproduction

Mice -- Fertility

Progesterone

Format

application/pdf

Number of Pages

79

Publisher

South Dakota State University

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