Gonadotropin plasma levels

Female rainbow trout, Oncorhynchusmykiss, also release in their urine 17,20jSP. As in goldfish, this pheromone increases the plasma levels of gonadotropin II and testosterone in spermiating males Scott etal, 1994). Levels of 17,20jSP rises within 1 hour of exposure and peak at 3-4 hours. Milt production also increases (Vermeirssenetfl /., 1997). 

Scott, A. P., Liley, N. R., and Vermeirssen, E. L. M. (1994). Urine of reproductively female rainbow trout, Oncorhynchus mykiss (Walbuam), contains a priming pheromone which enhances plasma levels of sex steroids and gonadotropin II in malts. Journal of Fish Biology 44,131-148. 

The second complicating factor is that multiple injections of GnRHa are often required to sustain sufficient levels of gonadotropins in the plasma, which further complicates this technique for tuna. An effective alternative to the use of multiple injections is to administer a slow-release implant that can maintain elevated plasma levels of gonadotropins for long periods (Mylonas, 2002 Mylonas et al, 2007). In 2004 and 2005, an agonist of GnRH prepared within a matrix of poly[Ethylene-Vinyl Acetate] (EVAc) was... 

More recently, it has been possible to directly measure the changes in gonadotropin levels in blood of experimental animals under various endocrinological conditions. The plasma levels of FSH and LSH increase within a week and reach a plateau within a month after ovariectomy. 

Harris, C.A., Santos, E.M., and Janbakhsh, A.P. et al. (2001). Nonylphenol affects gonadotropin levels in the pituitary gland and plasma of female rainbow trout. Environmental Science and Technology 35, 2909-2916. 

Under certain conditions, ovulation and plasma gonadotropin levels can be stimulated by ovarian fluid from other ovulated females. The African catfish, Clariasgaricpinus, is an example. It lives in muddy water and spawns at night, conditions expected to favor pheromone commimication. Moreover, this species is a seasonal breeder, spawning after rainfall. The sudden mass spawning requires synchronization. Water from males or ovulated females, and also ovarian fluid of ovulated females, experimentally induced ovulation in 67% of females. Plasma gonadotropin was also increased by these treatments (Resink etal., 1989c). 

When clomiphene is administered in doses of 100 mg/d for 5 days, a rise in plasma LH and FSH is observed after several days. In patients who ovulate, the initial rise is followed by a second rise of gonadotropin levels just prior to ovulation. 

M6. McLachlan, R. I., Healy, D. L., and Robertson, D. M., Plasma inhibin levels during gonadotropin-induced ovarian hyperstimulation for IVF A new index of follicular function ... 

Vermeulen, A. Dhondt, M. Thiery, M. Vandekerckhove, D. Plasma sex steroid and gonadotropin levels in control and silastic vaginal medroxyprogesterone acetate-impregnated ring cycles. Fertil. Steril. 1976, 27, 773-779. 

COMBINATION ORAL CONTRACEPTIVES Combination oral contraceptives act by preventing ovulation. Plasma LH and FSH levels are suppressed, the midcycle surge of LH is absent, endogenous steroid levels are diminished, and ovulation does not occur. While either component alone can exert these effects, the combination synergistically decreases plasma gonadotropin levels and suppresses ovulation more consistently than either alone. 

When hypophyses were transplanted in the kidneys of hypophysectomized animals, they were found to contain ACTH but were unable to release it. However, when the hypophysis is transplanted in the median eminence, the levels of plasma gonadotropins are maintained close to normal. Excision of most of the brain, except for the hypothalamus, has led to the conclusion that an intact median eminence and pituitary stalk complex is indispensable for normal activation of the adrenal by the pituitary. 

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