Our research at The University of Texas Medical Branch focuses on how the processes of aging influence the reproductive capabilites of mammals, especially factors which might relate to the human species. Our most recent studies have concentrated on how GnRH receptors change with age in cultured anterior pituitary cells of several age groups (6-, 14- and 23-25-month-old) of female C57BL/6NNia mice.
B.S. Biology, Midland College M.S. University of South Dakota Ph.D. University of Oregon Professor, Department of Anatomy & Neurosciences
and Obstetrics & Gynecology Cell Biology Graduate ProgramWe have been examining individual target cells by stimulating them with different forms of biotinylated GnRH in the cold and then attaching avidin-fluroescein for visualization with fluorescent microscopy or attaching avidin-gold, which has been silver-enhanced for visualization with a scanning electron microscope.
Figure 1 shows a scanning electron micrograph of a mouse anterior pituitary cell cultured for two days. The cell was exposed to biotinylated GnRH at 4 C for 1 hr., fixed and an avidin-gold complex with silver enhancement conjugated to the bound GnRH. The arrow represents the bound GnRH representative of a GnRH receptor. Figure 2 shows the same cell using back-scattering imagery for easier identification of the receptor sites (arrow)
To enhance the location of receptor sites for quantitation using the latter technique we have employed a back-scattering electron detector (see above photo). All of our studies are accompanied with radioimmunoassays to monitor the secretion of luteinizing hormone and follicle-stimulating hormone.
My laboratory is also collaborating with Dr. A. Bartke (Southern Illinois University) in using a transgenic mouse, they developed, which is a premature aging mouse. Mice which have had a bovine growth hormone gene inserted into their genome, when reaching 8-9 months of age resemble mice physiologically that are 23-24 months of age. This animal may prove to be an excellent model for studying all aging processes.
Pal, D., Collins, T.J. and Parkening, T.A. (1991) Levels of -inhibin in aging female mice. Biol. Reprod. 45:869-875.
Le, S., Chuong, C.J. and Parkening, T.A. (1991) Effect of ovariectomy and estrogen replacement on hypothalamic, pituitary and peripheral blood -endorphin levels in the rat. Neuropeptides 20:175-180.
Pal, D., Miller, B.T. and Parkening, T.A. (1992) Topographical mapping of GnRH receptors on dispersed mouse pituitary cells by backscattered electron imaging. Anat.Rec. 233:89-96.
Steger, R.W., Bartke, A., Parkening, T.A., Collins, T., Cerven, R., Yun, J.S. and Wagner, T.E. (1994) Effects of chronic exposure to bovine growth hormone (bGH) on the hypothalamic-pituitary axis in transgenic mice: relationship to the degree of expression of the PEPCK bGH hybrid gene. Transgenics 1:245-253.
Parkening, T.A., Pal, D. (1995) GnRH receptor sites increase on the surface of cultured gonadotropes of senescent C57BL/6NNia mice. J. Gerontol., in press.
Last updated: 5/14/97