摘要:

Pretreatment of confluent human fibroblast cultures for two days in dexamethasone, serum free medium increased 10 - 20 fold the sensitivity of the cells to insulin-like growth factor I (IGF I) stimulation of amino acid uptake using the amino acid analogα-aminoisobutyric acid (AIB). This increased sensitivity resulted both from the use of serum free medium and the addition of dexamethasone to the serum free media. Pretreatment of the cells for 1, 2. or 3 days before assay showed that the maximum increase in sensitivity was obtained after a two day pretreatment. Pretreatment of the cells also increased their sensitivity to insulin and bovine insulin-like growth factor II stimulation of AIB uptake similar to that seen for IGF I. No consistent effect of the pretreatment was observed on either the basal level of AIB uptake or the maximal hormonal stimulation of AIB uptake. Nor was any change noted in the shape of the dose response curves. Addition of IGF I to the pretreatment medium greatly reduced the sensitivity of pretreated cells. [125I]IGF I binding studies done on suspended fibroblasts indicated that there was up to a two fold increase in the number of receptors with no increase in their affinity for IGF I. Thus, pretreatment of fibroblasts with dexamethasone and serum free medium greatly enhances their sensitivity to IGF I stimulation of AIB uptake and makes this an excellent in vitro bioassay system for IGF I.

ISSN:0743-5800    

DOI:10.3109/07435808909042743

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

Female rats which were exposed to a single low dose of gamma irradiation (6R or 15R) at the age of 8 days produce smaller litters when mature than untreated controls. The possibility that such an impaired reproductive performance could result from changes in the endocrine system was investigated. Plasma levels and hypophyseal contents of LH and FSH, plasma levels of testosterone and hypothalamic content of GnRH were determined. The responsiveness of the pituitary to a single injection of GnRH (50 ng/rat) given on day of proestrus was evaluated. The results indicated that plasma levels of FSH but not of LH were lower in the irradiated rats. This was accompanied by changes in the hypothalamic content of GnRH. The possibility that the pituitary was sensitive to gamma irradiation was excluded. Twenty five minutes after a single injection of GnRH a 2-5 fold increase in LH plasma levels was noticed in all the groups, thus indicating that the reduced fertility could not be attributed to hypophyseal malfunction but rather to an impaired hypothalamic stimulus. Moreover, the lower levels of FSH might result from the significantly elevated levels of testosterone which were observed in the irradiated rats. Apparently, neonatal exposure to a single low dose of gamma irradiation resulted in a new hormonal equilibrium which was responsible for the reduced fertility in such rats.

ISSN:0743-5800    

DOI:10.3109/07435808909042744

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

The effect of clomiphene on nuclear estrogen receptors of the Fallopian tube during ovum transport in the rabbit has been studied. Nuclear binding capacity was observed in ampulla (A), ampullary-isthe±mic junction (AIJ), isthmus (I), uterine-isthmic junction (UIJ) and uterus (U). Receptor concentration decreased in all segments of the tube after administration of clomiphene in mated animals. The bindings are of high affinity and low capacity. Important alterations were observed during transport when compared to that of 14, 24, 34, 48, 72, 144 and 168 hrpost-coitum(p.c). At 24 hrp.cbinding increased only in I and decreased in A and AIJ. Retention of eggs at I at 24 hrp.cshowed as increase in binding at I. Egg transport was accelerated and eggs reached prematurely in the uterus due to the influence of clomiphene. Binding in I remained constent from 48 hrp.cto 144 hrp.cbut concurrently the binding level increased in U from 34 hr p.c. The elevation of nuclear estrogen receptor level was maximum at 24 hrp.cwhich coincided with increased plasma estrogen level. The result of such study showed that clomiphene depleted nuclear estrogen teceptor complex in the fallopian tube before transfer to the uterus. Further, observation indicated

ISSN:0743-5800    

DOI:10.3109/07435808909042745

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

Binding of gonadotropin-releasing hormone (GnRH) to the pituitary gonadotrope induces activation of a membrane associated calcium channel, resulting ultimately in luteinizing hormone release. The role of calcium mobilization in GnRH-induced follicle-stimulating hormone (FSH) release was explored using anterior pituitary glands from female rats in a perifusion tissue culture system. While perifusion with GnRH (10 ng/ml) induced a constant level of gonadotropin release, the calcium channel blocker verapamil (10-4M) depressed FSH release, as did dantrolene (10-4M), an antagonist of intracellular calcium mobilization. When the calcium ionophore A23187 (10-5M) was substituted for GnRH, FSH release was not only maintained but increased. Antagonism of the activity of calmodulin (CAM) with trifluoperazine (10-4M), however, did not depress FSH release. Cellular content of cAMP and cGMP increased in response to GnRH. When FSH secretion was ionophoretically induced by A23187, however, little cAMP was detected. These results support a role for calcium mobilization in the second messenger cascade underlying GnRH-induced FSH release. The role for calcium in the disparate release of FSH and LH were further discussed in the context of these data.

ISSN:0743-5800    

DOI:10.3109/07435808909042746

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

Recent data from many laboratories suggest that insulin stimulates diacylglycerol formation. Data presented in this manuscript demonstrate an insulin-like effect of PMA, a tumor promoting agent that mimics the action of diacylglycerol, in isolated adipocytes on; (a) glucose oxidation using uniformly labelled, C-1-labelled and C-6-labelled glucose, (b) epinephrine-induced lipolysis and (c) low Km cAMP phosphodiesterase activity. Additionally, a lipolytic effect of PMA is identified when unopposed by epinephrine. These data not only demonstrate an insulin-like effect of phorbol esters in adipose tissue but they lend support to the concept of diacylglycerol involvement in the mechanism of insulin action. This work was supported by research funds from the Veterans' Administration (SSS).

ISSN:0743-5800    

DOI:10.3109/07435808909042747

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

The question of whether ethanol's (ETOH's) known suppressive effect on serum luteinizing hormone (LH) could be mediated directly at the anterior pituitary level was addressed by examining the effects of ETOHin vitroon release of LH from cultured male rat pituitary cells. The impact of added ethanol concentrations ranging from 50 to 400 mg% on LH release was examined in the basal state and after stimulation by gonadotropin-releasing hormone (GnRH) at a dose of 5×10-10M. While ETOH did not significantly suppress basal LH release, secretion stimulated with GnRH was noted to be attenuated with higher doses of ETOH (±100 mg%) compared to stimulated control cells. It is concluded that ETOH exposurein vitroalters stimulated LH secretion by acting directly on pituitary gonadotropes.

ISSN:0743-5800    

DOI:10.3109/07435808909042748

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor

摘要:

Sustained subcutaneous administration of recombinant DNA-derived insulin-like growth factor II to immature female hypophysectomized rats stimulated significant increases in body weight gain, tibial epiphyseal cartilage width, femur hydroxyproline concentrations and a significant decrease in serum urea nitrogen concentrations. Recombinant DNA-derived human growth hormone (Humatrope), administered in the same manner produced similar biological effects. The data support the contention that hIGF-II has anabolic effects when administered to hypophysectomized rats and may be a locally acting mediator of pituitary hormone actions.

ISSN:0743-5800    

DOI:10.3109/07435808909042749

出版商:Taylor&Francis    

年代:1989

数据来源: Taylor