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L Kiesel

Publications and source records attributed to L Kiesel.

At least 37 records · Page 2Linked to original sources
PubMed1996

Role of leukotriene C4 in follicle-stimulating hormone (FSH) secretion in female rat pituitary.

Leukotriene C4, at doses of 0.01 and 0.1 nmol/l added to superfused cells in pulse of 4-min duration, evoked follicle-stimulating hormone (FSH) release up to 12- to 26-fold of basal secretion. Higher and lower concentrations of leukotriene C4 were not able to induce FSH secretion. Gonadotropin-releasing hormone (GnRH)-induced FSH release was reduced by 38-57% by the leukotriene receptor antagonist FPL 55712 (10 mumol/l). Moreover, we have shown that FSH release occurs parallel to leukotriene C4 synthesis in rat anterior pituitary cells. Mellitin (100 nmol/l), an activator of phospholipase A2, induced FSH and radioactivity secretion in rat anterior pituitary cells previously preincubated for 24 h with [3H]arachidonic acid (AA).

Animals↗
PubMed1996

Should add-back therapy for endometriosis be deferred for optimal results?

Add-back hormone replacement therapy has been shown to alleviate some of the hypo-oestrogenic side effects associated with gonadotrophin-releasing hormone agonists, including demineralisation of bone. Studies on patients with uterine fibroids have shown that concomitant add-back therapy reduced the efficacy of these agents, but that deferred administration was less detrimental. This trial set out to investigate if deferred add-back therapy could offer any advantages to patients with endometriosis compared with immediate therapy. Zoladex [goserelin acetate (3.6 mg every 4 weeks)] was given for 24 weeks either with placebo, with medrogestone (10 mg/day) for 24 weeks (immediate add-back therapy), or with placebo for 12 weeks followed by medrogestone (10 mg/day) for 12 weeks (deferred add-back therapy) to 123 patients. The number of responders measured using the Revised American Fertility Society score (decrease in this score of > or = 50%) was greatest in the immediate add-back therapy group, although there were no significant differences between groups. All three treatment groups showed significant decreases in bone mineral density compared with baseline but smaller losses were generally observed in the add-back groups. A significantly smaller number of patients in the immediate add-back group reported hot flushes during the first 12 weeks of treatment compared with the deferred add-back group. In conclusion, it appears that there is no extra advantage to patients with endometriosis being treated with goserelin in delaying the start of add-back therapy.

Bone Density↗
PubMed1995

Ovarian stimulation in women undergoing in-vitro fertilization and embryo transfer using recombinant human follicle stimulating hormone (Gonal-F) in non-down-regulated cycles.

In order to assess the efficacy and safety of recombinant human follicle stimulating hormone (FSH) in routine clinical use, ovarian stimulation with recombinant human FSH was performed in 71 patients prior to in-vitro fertilization (IVF) without gonadotrophin-releasing hormone (GnRH) analogues in a multicentre, non-comparative study. Human chorionic gonadotrophin (HCG) was administered to 58 patients (81.7%), 15 of whom underwent 19 cycles with an initial dosage of three ampoules daily of recombinant FSH and 43 of whom underwent 152 cycles with four ampoules daily from day 3 onwards. No significant differences were detected between these two groups in all test parameters. The mean duration of treatment was 9.06 and 8.86 days respectively with a mean number of 24.06 and 23.25 vials of recombinant human FSH administered. A mean number of 6.26 and 5.88 oocytes respectively was collected. The number of transferred embryos was 2.4 and 2.2. A clinical pregnancy rate of 23.8% (10 out of 42) per transfer was achieved (30.9 and 20.6% respectively). Local tolerance of s.c. administration was excellent. Mild pain at the injection site was the dominant finding in < 20% of patients. Two cases of ovarian hyperstimulation syndrome were noted. Recombinant human FSH is very attractive to patients because it can be self-administered s.c. and the preparation does not come from a human source. In conclusion, these data support the safety and efficacy of recombinant human FSH in routine use for IVF.

Adolescent↗
PubMed1993

Characterization of binding sites for a GnRH-agonist (buserelin) in human breast cancer biopsies and their distribution in relation to tumor parameters.

Gonadotropin-releasing hormone analogs (GnRH-A) have been added to the armentarium in the therapy of hormone-dependent breast cancer in premenopausal women. The effect of chronic GnRH-A-treatment in premenopausal women is based on the suppression of the hypothalamus-pituitary-ovarian axis and the reduction of sex-steroid serum levels. In addition, a number of experimental and clinical data have been accumulated indicating a direct action of GnRH-A on breast cancer cells and tissue. In this study we analyzed 235 human breast cancer biopsies for specific GnRH-A-binding. We demonstrate high affinity GnRH-A binding sites in human breast cancer tissues. The evaluation of clinical data showed no correlation of the level of GnRH-A-binding with classical tumor parameters.

Amino Acid Sequence↗
PubMed1993

Elevated serum inhibin levels and suppressed luteinizing hormone surge in young patients stimulated with gonadotropins.

The physiological role of inhibin and its relation to other sex hormones (estradiol, progesterone, follicle stimulating hormone (FSH) and luteinizing hormone (LH)) has been investigated during gonadotropin-stimulated cycles of 38 in vitro fertilization-embryo transfer/gamete intrafallopian transfer (IVF-ET/GIFT) patients. Human menopausal gonadotropin (hMG) was given from day 3 of the cycle until 1 day before ovulation induction with human chorionic gonadotropin (hCG). Blood samples were taken twice daily and hormone measurements performed by radioimmunoassay or enzyme immunoassay. Patients were divided into two groups: Group A comprised patients < 35 years of age (n = 20) and Group B included patients > or = 35 years of age (n = 18). The pregnancy rate was significantly higher in Group A. During the follicular phase, serum inhibin level rose gradually in both groups but the values were higher in Group A (significantly between days -2 and 0). During the early luteal phase serum inhibin concentrations were similar in both groups. Estradiol pattern did not differ in the two groups. Estradiol pattern did not differ in the two groups. Whilst serum estradiol level did not increase significantly after day 0, serum inhibin concentration reached its peak value 1 day later, on day +1. Serum progesterone was higher in Group A between days +1 and +4 (significantly on days +1, +3 and +4). Serum FSH increased slowly in both groups and did not correlate with serum inhibin concentration. Basal LH concentrations were similar between days -6 and -2 in both groups. Around the time of ovulation induction (day -1, 0 and +1) serum LH was lower in Group A (significantly on day 0).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

Molecular mechanisms of gonadotrophin releasing hormone-stimulated gonadotrophin secretion.

Hypothalamic gonadotrophin releasing hormone (GnRH) exerts its effect on gonadotrophin synthesis and release via plasma membrane-bound receptors. The exocytosis of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) is activated by the binding of GnRH or its agonists to receptors in pituitary cells, which initiates a number of post-receptor events within the gonadotroph cell. Various potential second messengers have been claimed to mediate the stimulatory action of GnRH including calcium, inositol phosphates, protein kinase C, arachidonic acid metabolites and cyclic nucleotides. It appears that more than one of these pathways is required to fully mimic the GnRH effect.

Animals↗
PubMed1992

Serum inhibin levels in gonadotrophin stimulated in-vitro fertilization/gamete intra-fallopian transfer cycles.

Serum inhibin concentrations of 64 cycles of in-vitro fertilization--embryo transfer (IVF-ET) or gamete intra-Fallopian transfer (GIFT) have been analysed retrospectively. No significant difference was observed in serum inhibin levels of cycles stimulated with buserelin and human menopausal gonadotrophin (HMG) or HMG alone. During the late follicular phase, serum inhibin was higher in cycles resulting in pregnancy than in cycles without a pregnancy (peak values on day +1: 8.3 versus 6.4 IU/ml, respectively). The same difference was found between stimulation cycles resulting in a viable or a non-viable pregnancy (peak values on day +1: 8.3 versus 7.5 IU/ml). However, these differences were not significant. During the early luteal phase, serum inhibin values were similar in these groups of patients. Our results indicate that the use of the gonadotrophin-releasing hormone (GnRH) analogue buserelin, in combination with HMG, for ovarian stimulation does not affect inhibin production by granulosa cells in vivo. The late follicular and early luteal concentrations of serum inhibin have to be considered unsuitable as predictors in IVF/GIFT cycles with respect to pregnancy and pregnancy outcome.

Adult↗
PubMed1992

[Gonadotropin releasing hormone and analogs. Physiology and pharmacology].

The natural gonadotropin-releasing hormone (GnRH) is secreted by hypothalamic neurons and acts at the level of anterior pituitary gonadotrophs releasing the peptides luteinizing hormone and follicle-stimulating hormone. GnRH is a decapeptide sensitive to peptidases, resulting in a short half-life. The synthesis of highly potent analogues of GnRH provides peptides with a longer half-life and a higher affinity to the GnRH-receptor. The presently available GnRH analogues for clinical use act initially as agonists by upregulating GnRH receptors in the pituitary. A few days after continuous application of GnRH analogues down-regulation of receptors and desensitization of the pituitary occur. In addition to receptor mechanisms, a number of postreceptor actions at the level of second messengers (protein kinase C, leukotriene and inositol phosphates) are responsible for the inhibition of adequate gonadotropin secretion. This paradoxical entire fertility action of the analogues is the basic principle for its clinical use, resulting in a reversible suppression of pituitary and thereby ovarian function.

Animals↗
PubMed1991

Production of leukotrienes in gonadotropin-releasing hormone-stimulated pituitary cells: potential role in luteinizing hormone release.

Gonadotropin-releasing hormone (GnRH) stimulated the formation of two major metabolites of the 5-lipoxygenase pathway, leukotriene (LT) B4 and LTC4, as well as luteinizing hormone (LH) release in primary cultures of rat anterior pituitary cells. Several lines of evidence suggested the presence of a GnRH-dependent pituitary endocrine system in which LTs act as second messengers for LH release: (i) GnRH-dependent LT formation was observed within 1 min and immediately preceded GnRH-induced LH release, whereas exogenous LTs stimulated LH release at low concentrations; (ii) the dose responses of GnRH-induced LT production and LH release were similar and both effects required the presence of extracellular Ca2+ ions; (iii) GnRH-induced LH release was blocked by up to 45% following the administration of several LT receptor antagonists; (iv) LTE4 action on LH secretion was entirely abolished by LT receptor antagonists; and (v) an activator of protein kinase C acted synergistically with LTE4 to induce LH release. The major source of LT formation in the pituitary cell cultures appeared to be the gonadotrophs, as shown by GnRH receptor desensitization experiments. The results demonstrate the presence of a GnRH-activatable 5-lipoxygenase pathway in anterior pituitary cells and provide strong support for the hypothesis that LTs play a role in LH release in the GnRH signaling pathway.

Animals↗
PubMed1991

Characterization of leukotriene C4 binding in anterior pituitary membrane preparations.

Pituitary cells produce leukotrienes (LTs) and respond to exogenous administration of LTs by releasing gonadotropins. Specific high affinity leukotriene C4 (LTC4) binding has been found in membrane preparations of bovine anterior pituitaries. Unlabelled LTC4 displaced specific [3H]LTC4 binding. Other leukotrienes (LTB4, LTD4, LTE4, LTF4) did not compete with [3H]LTC4 for binding sites when administered at increasing concentrations together with a constant amount of radioligand indicating that the binding is highly specific for LTC4. Scatchard analysis of binding data obtained from saturation studies revealed a single binding site for [3H]LTC4 with a Kd of 8.95 +/- 5.53 nM and a B max of 15.44 +/- 6.93 pmol per mg of membrane protein. Glutathione S-transferase, a possible LTC4 binding site, did not display activity in the membrane fraction although the two glutathione derivates S-octylglutathione and S-decylglutathione competed with LTC4 in binding experiments. As leukotrienes are potent stimulators of gonadotropin secretion and modulators of gonadotropin-releasing hormone (GnRH)-induced gonadotropin release it is concluded that leukotrienes may be involved in the signal transduction pathway of GnRH and that they may act via a specific and high affinity receptor.

Animals↗
PubMed1991

High preovulatory serum luteinizing hormone level is unfavorable to conception.

Serum estradiol, progesterone and luteinizing hormone (LH) levels of 16 pregnant and 58 non-pregnant stimulated in vitro fertilization-embryo transfer (IVF-ET) or gamete intrafallopian transfer (GIFT) cycles have been compared with regard to their predictive value for achievement of pregnancy. Serum estradiol and progesterone pattern of the pregnant and non-pregnant group did not show any significant difference. Around the time of ovulation induction by human chorionic gonadotropin (hCG) the serum LH values proved to be higher in the non-pregnant group than in the pregnant one. In spite of having a permissive function, preovulatory serum estradiol and progesterone seem not to have a predictive value with regard to pregnancy. Elevated preovulatory serum LH is detrimental for pregnancy, therefore the measurement of serum LH beyond hCG administration also, and the cancellation of cycles with high serum LH levels shortly before oocyte retrieval is recommended.

Adult↗
PubMed1991

LH-RH receptors in the human pancreas. Basis for antihormonal treatment in ductal carcinoma of the pancreas.

LH-RH-, estrogen-, and progesterone-receptor binding was measured in the human pancreas of patients with ductal pancreatic cancer (n = 23) and chronic pancreatitis (n = 15), and of organ donors (n = 11). Receptor analysis was determined by incubation of the homogenized tissues with estrogen, progesterone, and the LH-RH analog buserelin labeled with iodine-125. Only one biopsy (9%) from normal pancreas had an LH-RH-receptor concentration greater than 3 fmol/mg membrane protein. LH-RH binding levels greater than 3 fmol/mg were detected in 67% of patients with chronic pancreatitis and in 57% of patients with pancreatic cancer. Progesterone levels greater than 15 fmol/mg membrane protein were found in 36% of normal pancreas, in 27% of chronic pancreatitis, and in 17% of pancreatic cancer cases, respectively. The highest concentration of estrogen receptors (greater than 15 fmol/mg membrane protein) was seen in normal pancreas (73%). The increase in LH-RH-receptor concentration in chronic pancreatitis and pancreatic cancer seems to be unspecific, but might be of benefit for antiproliferative treatment in pancreatic cancer.

Adult↗
PubMed1990

Differences in luteinizing hormone release stimulated in rat anterior pituitary cells by leukotriene C4 and by gonadotropin-releasing hormone in vitro.

Continuous administration of leukotriene C4 (LTC4, 10(-10) M) to superfused rat anterior pituitary cells increased LH release for 40 min only, whereas in a parallel experiment gonadotropin-releasing hormone (GnRH, 10(-9) M) evoked a continuous increase in hormone secretion. In contrast to GnRH, LTC4 did not desensitize rat anterior pituitary cells. The secretory action resulting from the administration of LTC4 (10(-10) M) was abolished for 40 min after previous stimulation. The results documented the dual action of LTC4 on LH exocytosis.

Animals↗
PubMed1990

Exogenous action of 5-lipoxygenase by its metabolites on luteinizing hormone release in rat pituitary cells.

The stimulatory effect of exogenously administered potato 5-lipoxygenase (0.1-0.3 U/2 ml) on luteinizing hormone (LH) release was demonstrated in rat anterior pituitary cells in a superfusion system. Nordihydroguaiaretic acid (NDGA), an inhibitor of 5-lipoxygenase, abolished the effect of the enzyme on LH secretion. The secretory effect on LH after 5-lipoxygenase administration was biphasic and dependent on Ca2+ indicating that 5-lipoxygenase affects LH release through its oxygenation reaction. Another series of experiments demonstrated that activation of 5-lipoxygenase, expressed as production of leukotriene (LT) B4 and C4 (728 +/- 127 pg/10(6) cells and 178 +/- 23 pg/10(6) cells, respectively) occurs in rat pituitary cells after addition of Ca2+ ionophore A23187. However, LTB4 and LTC4 were not formed by pituitary cells that had previously been desensitized by gonadotropin-releasing hormone (GnRH), the physiological ligand of LH release. These results are consistent with a role of 5-lipoxygenase metabolites in the mechanism of GnRH-induced LH secretion.

Animals↗