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  • 1
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Phytoestrogens can produce inhibitory effects on gonadotropin secretion in both animals and humans, although little is known about the mechanisms and the role of direct action on oestrogen receptors (ER) in this process. We examined the effect of coumestrol, alone and combined with ER antagonists, on gonadotropin-releasing hormone (GnRH) mRNA expression in GT1-7 cells. Coumestrol was found to have an inhibitory effect compared to controls, which was blocked by R,R-THC, a selective ERβ antagonist. These results suggest that ERβ is involved in the suppression of GnRH mRNA expression by coumestrol.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Recent evidence has shown calcitonin gene-related peptide (CGRP) to be a key mediator of stress-induced suppression of the gonadotrophin-releasing hormone (GnRH) pulse generator, although little is known about the neural pathways involved. In the present study, we investigated the potential direct action of CGRP on GnRH neurones using GT1-7 cells, an established GnRH cell line. First, we detected expression of the CGRP receptor subunits, calcitonin receptor-like receptor and receptor activity-modifying protein-1 in the GT1-7 cells by reverse transcriptase-polymerase chain reaction. Second, we have shown that CGRP inhibits GnRH mRNA expression in the GT1-7 cells, which was effectively reversed by the CGRP receptor antagonist, CGRP8-37. These results suggest that CGRP down regulates expression of GnRH mRNA, via CGRP receptors in the GT1-7 cell, thus implying that a potential direct action of CGRP may mediate a suppressive effect on the GnRH neural network.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Stress activates the hypothalamic-pituitary-adrenocortical (HPA) axis and can suppress pulsatile luteinizing hormone (LH) secretion, resulting in reproductive dysfunction. The histocompatible inbred Fischer and Lewis rat strains exhibit marked phenotypic differences in the activity of the HPA axis, the former being more reactive. Using Fischer, Lewis and Wistar rats, we assessed effects of repeated restraint stress on pulsatile LH secretion. Adult rats were ovariectomized and fitted with cardiac catheters. Blood samples were collected at 5-min intervals for 3–5 h for detection of LH. Less frequent samples were collected for corticosterone measurement. After 2 h, rats were restrained for 60 min. The same regimen was repeated four times at 6-day intervals. The mean peak corticosterone levels achieved during the first restraint in Fischer rats were significantly higher than those in Lewis and Wistar rats. By the time of the fourth episode of restraint, there had been some adaptation of the corticosterone response in the Fischer, but not in the Lewis or Wistar rats. LH pulses were interrupted during the 1st restraint in all experimental groups, although only Fischer rats showed suppression of LH pulses during the subsequent 2-h postrestraint period. During the fourth restraint, LH pulse frequency was still reduced in Wistar, but not in Fischer and Lewis rats, both of which showed a complete habituation. These results suggest that differential control mechanisms underlie the response of the HPA and HPG axes to repeated restraint stress.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1365-2826
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Corticotropin-releasing hormone (CRH) is implicated in the suppression of pulsatile luteinizing hormone (LH) secretion by a variety of stressful stimuli; 17β-oestradiol (E2) has been shown to modulate this inhibitory response. The present study in ovariectomized (OVX) rats was designed to investigate the effect of E2 and progesterone (P4) on hypoglycaemic stress-induced changes in pulsatile LH secretion and on the associated changes in both central and peripheral components of the hypothalamic-pituitary-adrenal axis. E2 enhanced the hypoglycaemic stress-induced suppression of LH pulses; P4 in addition to E2 further potentiated the inhibitory response. The rise in plasma corticosterone following insulin-induced hypoglycaemia (IIH) was highest in the E2 + P4 group. Nevertheless, when such levels were achieved by administration of corticosterone, the occurrence of LH pulses was completely unaffected, irrespective of ovarian steroid milieu. E2 and E2 + P4 up-regulated basal CRH mRNA expression in the paraventricular nucleus (PVN) as measured by in situ hybridization; this signal was also increased in the medial preoptic nucleus (MPN) following E2. IIH resulted in a rise in CRH mRNA in the PVN, but not in the MPN; this rise may reflect a more significant role for the PVN in the present context. Changes in neuropeptide mRNA expression may signal changes in neuronal activity; nevertheless, the profound differences in LH pulse suppression in OVX, E2 and E2 + P4 rats following IIH were not reflected in the concurrent changes in CRH mRNA in the PVN. The results suggest that while corticosterone has no acute effect on LH pulses in the rat, the up-regulation by ovarian steroids of basal CRH mRNA in the PVN and/or MPN may contribute to the central regulation of these pulses in response to stress.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [s.l.] : Nature Publishing Group
    Nature 309 (1984), S. 372-374 
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Rats were taken from the departmental colony where they had been housed in an environment of controlled light and temperature, with water and food available ad libitum. The day of delivery was denoted as day 1, and the animals were used between days 8 and 12 of lactation. The protocol for these ...
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  • 6
    ISSN: 1569-8041
    Keywords: concentration-controlled ; etoposide ; randomised ; small-cell lung cancer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Purpose: This randomised trial was designed to investigate the activity and toxicity of continuous infusion etoposide phosphate (EP), targeting a plasma etoposide concentration of either 3 µg/ml for five days (5d) or 1 µg/ml for 15 days (15d), in previously untreated SCLC patients with extensive disease. Patients and methods: EP was used as a single agent. Plasma etoposide concentration was monitored on days 2 and 4 in patients receiving 5d EP and on days 2, 5, 8 and 11 in patients receiving 15d EP, with infusion modification to ensure target concentrations were achieved. Treatment was repeated every 21 days for up to six cycles, with a 25% reduction in target concentration in patients with toxicity. Results: The study has closed early after entry of 29 patients (14 with 5d EP, 15 with 15d EP). Objective responses were seen in seven of 12 (58%, confidence interval (CI): 27%–85%) evaluable patients after 5d EP, and two of 14 (14%, CI: 4%–42%) evaluable patients after 15d EP (P = 0.038). Grade 3 or 4 neutropenia or leucopenia during the first cycle of treatment was observed in six of 12 patients after 5d EP and 0/14 patients after 15d EP (P = 0.004), with median nadir WBC count of 2.6 × 109/l after 5d and 5.0 × 109/l after 15d EP (P = 0.017). Only one of 49 cycles of 15d EP was associated with grade 3 or worse haematological toxicity, compared to 14 of 61 cycles of 5d EP. Conclusions: Although the number of patients entered into this trial was small, the low activity seen at 1 µg/ml in the 15d arm suggests that this concentration is below the therapeutic window in this setting. Further concentration-controlled studies with prolonged EP infusions are required.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 1569-8041
    Keywords: chemotherapy ; colorectal cancer ; 5-fluorouracil ; folinic acid ; hydroxyurea ; modulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: Hydroxyurea (HU), an inhibitor of ribonucleotide reductase, may potentiate the activity of 5-fluorouracil (5-FU) and folinic acid (FA) by reducing the deoxyribonucleotide pool available for DNA synthesis and repair. However as HU may inhibit the formation of 5-fluoro-2′-deoxyuridine-5′-monophosphate (FdUMP), one of the principal active metabolites of 5-FU, the scheduling of HU may be critical. In vitro experiments suggest that administration of HU following 5-FU, maintaining the concentration in the region of 1 mM for six or more hours, significantly enhances the efficacy of 5-FU. Patients and methods: 5-FU/FA was given as follows: days 1 and 2 – FA 250 mg/m2 (max. 350 mg) over two hours followed by 5-FU 400 mg/m2 by intravenous bolus (ivb) over 15 minutes and subsequently 5-FU 400 mg/m2 infusion (ivi) over 22 hours. HU was administered on day 3 immediately after the 5-FU with 3 g ivb over 15 minutes followed by 12 g ivi over 12 hours. Results: Thirty patients were entered into the study. Median survival was nine months (range 1–51+ months). There were eight partial responses (28%, 95% CI: 13%–47%). The median duration of response was 6.5 (range 4–9 months). Grade 3–4 toxicities included neutropenia (grade 3 in eight patients and grade 4 in five), anaemia (grade 3 in one patient) and diarrhoea (grade 3 in two patients). Neutropenia was associated with pyrexia in two patients. Phlebitis at the infusion site occurred in five patients. The treatment was complicated by pulmonary embolism in one patient and deep venous thrombosis in another. Conclusion: HU administered in this schedule is well tolerated. Based on these results and those of other phase II studies, a randomised phase III study of 5-FU, FA and HU versus 5-FU and FA using the standard de Gramont schedule is recommended.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Regulatory Peptides 51 (1994), S. 276 
    ISSN: 0167-0115
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Medicine
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1569-8041
    Keywords: advanced gastric cancer ; mitomycin C ; oral etoposide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Background: Mitomycin C and etoposide have both demonstrated activityagainst gastric carcinoma. Etoposide is a topoisomerase II inhibitor withevidence for phase-specific and schedule-dependent activity. Patients and method: Twenty-eight consecutive patients with advancedupper gastrointestinal adenocarcinoma were treated with intravenous (i.v.)bolus mitomycin C 6 mg/m2 on day 1 every 21 days to a maximumof four courses. Oral etoposide capsules 50 mg b.i.d. (or 35 mg b.i.d. liquid)were administered days 1 to 10 extending to 14 days in subsequent courses ifabsolute neutrophil count 〉1.5 × 109/l on day 14 offirst course, for up to six courses. Results: Twenty-six patients were assessed for response of whom 12had measurable disease and 14 evaluable disease. Four patients had adocumented response (one complete remission, three partial remissions) withan objective response rate of 15% (95% confidence interval(95% CI) 4%–35%). Eight patients had stable diseaseand 14 progressive disease. The median survival was six months. The schedulewas well tolerated with no treatment-related deaths. Nine patients experiencedleucopenia (seven grade II and two grade III). Nausea and vomiting (eightgrade II, one grade III), fatigue (eight grade II, two grade III) and anaemia(seven grade II, two grade III) were the predominant toxicities. Conclusion: This out-patient schedule is well tolerated and showsmodest activity in the treatment of advanced upper gastrointestinaladenocarcinoma. Further studies using protracted schedules of etoposide bothorally and as infusional treatment should be developed.
    Type of Medium: Electronic Resource
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