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Results for “Luteinization”

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PubMed2003

[Expression of telomerase in human ovarian luteinized granulosa cells and its relationship to ovarian function].

OBJECTIVE: To detect the expression of telomerase catalytic subunit (TERT), telomerase in human ovarian luteinized granulosa cells and to investigate the relationship between telomerase expression and the ovarian fecundity. METHODS: Ovarian luteinized granulosa cells were recovered from 22 women with regular menses who underwent in vitro fertilization/intracytoplasmic sperm injection programme. We carried out in situ hybridization histochemistry on luteinized granulosa cells to detect TERT mRNA expression, and telomeric repeat amplification protocol to detect telomerase activity. RESULTS: TERT mRNA were present in luteinized granulosa cells. The expression of TERT mRNA and telomerase activity in ovarian luteinized granulosa cells decreased with increase of age, basal serum follicle stimulating hormone levels. CONCLUSIONS: These results suggest that telomerase may play an active role in ovarian function.A reduced telomerase activity of granulosa cells may be one of the important mechanisms involved in decreased ovarian function in women.

Adult↗

PubMedDate not supplied

Anatomical relationships of monoaminergic and neuropeptide Y-containing fibres with luteinizing hormone-releasing hormone systems in the preoptic area of the sheep brain: immunohistochemical studies.

Immunohistochemical double-labellings of luteinizing hormone-releasing hormone and neuropeptide Y, serotonin, tyrosine hydroxylase and dopamine-beta-hydroxylase, were performed in the preoptic area at the level of the organum vasculosum laminae terminalis. The observed neuropeptide Y-, serotonin-, tyrosine hydroxylase- and dopamine-beta-hydroxylase-immunoreactive fibres presented large varicosities when they were found within close proximity to luteinizing hormone-releasing hormone-containing perikarya. The fact that neuropeptide Y- and dopamine-beta-hydroxylase-immunoreactive fibres exhibited the same morphological characteristics and the comparison of the distribution of these two fibre populations raised the possibility of the co-localization of neuropeptide Y and dopamine-beta-hydroxylase in the same fibres. Dopamine-beta-hydroxylase- and tyrosine hydroxylase-immunoreactive fibres were morphologically different, suggesting that both dopaminergic and noradrenergic fibres could contact luteinizing hormone-releasing hormone-containing perikarya. Serotonin-immunoreactive fibres were also found close to the perikarya and to the proximal dendrite of the luteinizing hormone-releasing hormone-containing neurons. This study showed only putative sites of interactions between chemically identified fibres and luteinizing hormone-releasing hormone-containing neurons. Further ultrastructural immunocytochemical investigations are needed to ascertain the existence of synaptic contacts.

Animals↗

PubMed1985

[Functional interrelationship between granulosa and theca lutein cells in steroidogenesis in vitro by human corpus luteum].

To investigate the interrelation between steroidogenic function of granulosa and theca lutein cells of the human corpus luteum, twelve corpora lutea of menstruation and pregnancy were divided into inner and outer layers, each of which was histologically confirmed to be composed of pure granulosa lutein cells (GL) or GL plus theca lutein cells (TL), respectively. Slices of each layer were incubated with radioactive pregnenolone, 17-hydroxyprogesterone and androstenedione respectively, and the metabolites were analysed by reverse dilution technique with recrystallization to constant specific activity. Both slices converted pregnenolone-14C to progesterone, 17-hydroxyprogesterone, androstenedione, estrone and estradiol-17 beta, with progesterone being the major steroid formed. Formation of progesterone was significantly pronounced in the case of slices from the inner layer, while conversion into the other steroids was significantly higher in the case of slices from the outer layer. Formation of androstenedione from 17-hydroxyprogesterone-14C was also greater with the outer slices than the inner slices. However, conversion of androstenedione-14C to radioactive estrone and estradiol-17 beta was more efficient with the inner slices than the outer slices. These results suggest that the activity of aromatizing enzymes is higher in granulosa lutein cells, while that of 17 alpha-hydroxylase and C17-C20 lyase is higher in theca lutein cells. Therefore, cooperation of the two cell types would be necessary for the fulfillment of the function of estrogen biosynthesis by human corpus luteum.

Adult↗

PubMed1995

Regulation of 72-kd type IV collagenase-matrix metalloproteinase-2 by estradiol and gonadotropin-releasing hormone agonist in human granulosa-lutein cells.

OBJECTIVE: To examine the hormonal regulation of 72-kd type IV collagenase-gelatinase-matrix metalloproteinase-2 in human granulosa-lutein cells. DESIGN: The effect of E2 and GnRH agonist (GnRH-a) on matrix metalloproteinase-2 amount was examined on a long-term granulosa-lutein cell cultures. PATIENTS: The preovulatory follicles from women participating in our IVF program were aspirated through the vaginal wall. Follicular fluids were centrifuged and the granulosa cells were separated and pooled for culturing. MAIN OUTCOME MEASURES: Matrix metalloproteinase-2 enzyme activity was assayed with type IV collagen degradation assay and zymography. The matrix metalloproteinase-2 immunoreactive protein was studied by using specific antibodies. RESULTS: Matrix metalloproteinase-2 was the predominant form of gelatinase in cultured granulosa-lutein cells. The enzyme activity as well as the immunoreactive protein increased in the culture medium of the granulosa-lutein cells in the presence of E2. The effect of E2 was abolished by GnRH-a. CONCLUSIONS: Estradiol regulates the matrix metalloproteinase-2 enzyme amount in granulosa-lutein cells; the effect may be antagonized by GnRH-a.

Cells, Cultured↗

PubMed1995

Role of calcium in luteinization stimulator-enhanced progesterone production of porcine granulosa cells.

Intrafollicular luteinization stimulator was shown to be secreted by granulosa cells in culture with stimulatory effects on differentiation of immature granulosa cells. The purpose of this study was to evaluate the role of calcium ions in luteinization stimulator-enhanced luteinization process of granulosa cells. We examined the direct effect of ionophore A23187, voltage-sensitive Ca(2+)-channel blockers verapamil, nimodipine, nifedipine, niludipine and calmodulin antagonist trifluoroperazine on progesterone and cGMP levels in 3-day culture of small granulosa cells. It was shown that the dihydropyridine derivates of calcium blocker drugs (nimodipine, nifedipine, niludipine) and calmodulin antagonist (trifluoroperazine) in the micromolar range, significantly suppressed FSH-induced progesterone synthesis and cGMP accumulation in granulosa cells. On the contrary, phenylalkylamine calcium blocker verapamil and calcium ionophore A23187 had different effects on both processes. Calcium ionophore A23187 markedly enhanced cGMP formation, but simultaneously inhibited the FSH-induced progesterone synthesis. Verapamil at lower concentrations (10 microM) stimulated and at higher concentrations (50 microM) inhibited the formation of cGMP. To evaluate the role of extra- and intracellular calcium in luteinization stimulator-enhanced progesterone production by small granulosa cells, the effects of indicative agents on stimulatory activity of follicular fluid from large follicles, granulosa cells-conditioned media and granulosa cell extracts were tested. While verapamil is shown to be a less potent modulator, administration of other calcium antagonists as well as ionophore A23187 caused a significant decrease in stimulatory action of follicular fluid from large follicles, granulosa cells-conditioned media and extracts. These findings indicate that the stimulatory action of luteinization stimulator depends on the transport of calcium ions through voltage-sensitive calcium channels and is modulated by alteration of intracellular calcium levels.

Animals↗

PubMed2002

Morphological analyses of interleukin-8 effects on rat ovarian follicles at ovulation and luteinization in vivo.

The aim of the present study was to elucidate functions of the interleukin (IL)-8 at ovulation and luteinization in vivo. To compare the morphological differences between human chorionic gonadotropin (hCG) and IL-8 stimulation, scanning electron microscopy was employed to study rat ovarian vascular corrosion casts. Follicular growth and increased capillary vessel densities around the follicles were seen in vascular corrosion casts after IL-8 injection, similar to the result of hCG administration. This result indicated that exogenous IL-8 could play a role in the neovascularization during follicular development as an angiogenetic factor. Many fenestrations were observed in the vascular endothelium by hCG administration. In contrast, no fenestrations were observed with IL-8 injection, indicating that IL-8 may not be sufficient to increase the vascular permeability directly. Although germinal vesicle breakdown (GVBD) occurred at rates of 82% after the hCG injection, only 20% GVBD was observed after the IL-8 injection. The present study indicated that IL-8 might have important effects on rat follicles at ovulation and luteinization via vascularization in a similar manner to hCG. However, IL-8 was not effective on vascular permeability and oocyte maturation, which were different from hCG. Thus, we can conclude that IL-8 can participate in follicular development in part and may play important roles in ovulation and luteinization as one of some mediators induced by endogenous luteinizing hormone.

Animals↗

PubMed2004

Premature luteinization defined as progesterone estradiol ratio >1 on hCG administration day seems to adversely affect clinical outcome in long gonadotropin-releasing hormone agonist cycles.

AIM: To examine the effect of premature luteinization on the outcomes in long gonadotropin-releasing hormone agonist cycles. METHODS: Two-hundred and forty-eight patients who had undergone assisted reproductive technology for infertility treatment between 2001 and 2002 were enrolled into the study. The patients were separated into two groups according to P/E2 ratios on human chorionic gonadotropin administration day. Group A consisted of the patients whose P/E2 ratio was 1 (n = 116) and Group B consisted of the patients with premature luteinization of which P/E2 ratio was > 1 (n = 132). The P/E2 ratio calculation was performed as follows: P (in ng/mL) x dagger 1,000/E2 (in pg/mL). The primary outcome measures included oocyte quality, fertilization rates and clinical pregnancy rates. RESULTS: The mean number of mature oocytes retrieved in the groups were 9.5 +/- 4.8 and 6.4 +/- 3.6, respectively, and the difference was statistically significant (P < 0.05). Although the difference between the fertilization rates in Group A and Group B was not statistically significant (P > 0.05), the clinical pregnancy rates seemed to be affected adversely in the Group B patients with premature luteinization (41.4%versus 28%, respectively; P < 0.05). CONCLUSION: Premature luteinization, defined as P/E2 > 1 on human chorionic gonadotropin administration day, in long gonadotropin-releasing hormone agonist cycles seems to adversely affect clinical outcome.

Chorionic Gonadotropin↗

PubMed1998

Antioxidant activity of carotenoids: an electron-spin resonance study on beta-carotene and lutein interaction with free radicals generated in a chemical system.

beta-Carotene is thought to be a chain-breaking antioxidant, even though we have no information about the mechanism of its antioxidant activity. Using electron-spin resonance (ESR) spectroscopy coupled to the spin-trapping technique, we have studied the effect of beta-carotene and lutein on the radical adducts of the spin-trap PBN (N-t-butyl-alpha-phenylnitrone) generated by the metal-ion breakdown of different tert-butyl hydroperoxide (tBOOH) concentrations in methylene chloride. The peroxyl radical, along with an oxidation product of PBN (the PBNOx), trapped at room temperature from the breakdown of high concentration of tBOOH (1 M), were quenched by beta-carotene or lutein, in competition with the spin-trapping agent. However, carotenoids were not able to quench the alkoxyl and methyl radicals generated in the reaction carried out in the presence of low tBOOH concentration (1 mM). The reaction between carotenoids and the peroxyl radical was also carried out in the absence of the spin trap, at 77 K: Under these different experimental conditions, we did not detect any radical species deriving from carotenoids. In the same system, a further evidence of the peroxyl radical quenching by beta-carotene and lutein was obtained. The antioxidant activity of vitamin E was also tested, for comparison with the carotenoids. In the presence of alpha-tocopherol, peroxyl and alkoxyl radicals were quenched, and the tocopheroxyl radical was detected. Our data provide the first direct evidence that carotenoids quench peroxyl radicals. Under our experimental conditions, we did not detect any carotenoid radical species that could derive from the interaction with the peroxyl radical. The radical-trapping activity of beta-carotene and lutein demonstrated in this chemical reaction contributes to our understanding carotenoid antioxidant action in biological systems.

Antioxidants↗

PubMed1997

Distribution of lutein and zeaxanthin stereoisomers in the human retina.

The distribution of macular pigment stereoisomers in the human retina has been mapped and a pathway to account for the presence of the non-dietary carotenoid, meso-zeaxanthin, is proposed. Adult neural retinas were cut into three concentric areas centered on the fovea, and the extracted carotenoids were analysed and purified by high-performance liquid chromatography. The dicarbamate or dibenzoate derivatives of the collected zeaxanthin fractions for each tissue sample were further analysed by HPLC to determine their stereoisomer composition. Whole retinas from infant eyes were similarly analysed. The results show that, relative to zeaxanthin, the concentration of lutein in the adult neural retina increases with radial distance from the fovea while that of meso-zeaxanthin decreases. Infant retinas were found to have more lutein and less meso-zeaxanthin, relative to zeaxanthin, than adult retinas. Small quantities of (3S, 3'S)-zeaxanthin were also found in the adult retina, particularly in the macula. It is proposed that lutein and zeaxanthin are transported into an individual's retina in the same proportions found in his or her blood serum. Some of the lutein is then converted into meso-zeaxanthin, primarily in the macula, by a mechanism which is less developed in infants than adults.

Age Factors↗

PubMed1995

Plasma prolactin and luteinizing hormone during termination and onset of photorefractoriness in intact and pinealectomized European starlings (Sturnus vulgaris).

Plasma levels of prolactin and luteinizing hormone have been examined in intact and pinealectomized European starling (Sturnus vulgaris) during termination and onset of photorefractoriness. Photorefractory starlings exposed to long (18L:6D) daily photoperiods for 10 weeks were pinealectomized. One week after pinealectomy these birds, along with the intact and sham-operated birds, were transferred to short (8L:16D) daily photoperiods. After 10 weeks on short day lengths the daily photoperiod was switched to long (18L:6D) and the birds remained on this regime for a further 10 weeks. Plasma prolactin and luteinizing hormone were determined prior to pinealectomy and then weekly throughout the experiment. Molt scores were also recorded. Profiles of both the hormones and the molt pattern were similar in pinealectomized, sham-operated, and intact control starlings. In European starlings the pineal gland does not seem to exert significant effects on the photoinduced rise in plasma prolactin and luteinizing hormone seen in photosensitive birds. It is also suggested that pinealectomy has no significant effect on the dissipation and onset of photorefractoriness assessed from plasma luteinizing hormone secretion in this bird.

Animals↗

PubMed2002

[Objective determination of optical density of xanthophyll after supplementation of lutein].

BACKGROUND: It is thought that a high optical density of xanthophyll has a protective effect against the development of aggregated macular degeneration. The aim of this study was to investigate whether an increase of the optical density of xanthophyll in the macula after a supplementation of lutein can be proven by objective methods. Most methods applied for the determination of the macular pigment require the co-operation of the proband and the ability for foveal fixation. METHOD: Imaging spectrometry and the evaluation of laser scanner images taken at 488 nm will be presented. In contrast to psychophysical methods, both methods are independent of the patients ability for foveal fixation. RESULTS: Even by evaluation of laser scanner images taken as in fluorescence angiography but without inserting the blocking filter, the 2-dimensional distribution of xanthophyll can be determined. In 10 probands taking 6 mg lutein daily over 40 days, an increase of the optical density could be determined at least in some probands. The optical density reached a plateau 30 days after starting the supplementation of lutein. CONCLUSION: The assumed protective effect of xanthophyll against age-related macular degeneration can be influenced by supplementation of lutein under objective control.

Adult↗

PubMed2003

Occurrence of the lutein-epoxide cycle in mistletoes of the Loranthaceae and Viscaceae.

The lutein-epoxide cycle (Lx cycle) is an auxiliary xanthophyll cycle known to operate only in some higher-plant species. It occurs in parallel with the common violaxanthin cycle (V cycle) and involves the same epoxidation and de-epoxidation reactions as in the V cycle. In this study, the occurrence of the Lx cycle was investigated in the two major families of mistletoe, the Loranthaceae and the Viscaceae. In an attempt to find the limiting factor(s) for the occurrence of the Lx cycle, pigment profiles of mistletoes with and without the Lx cycle were compared. The availability of lutein as a substrate for the zeaxanthin epoxidase appeared not to be critical. This was supported by the absence of the Lx cycle in the transgenic Arabidopsis plant lutOE, in which synthesis of lutein was increased at the expense of V by overexpression of epsilon-cyclase, a key enzyme for lutein synthesis. Furthermore, analysis of pigment distribution within the mistletoe thylakoids excluded the possibility of different localizations for the Lx- and V-cycle pigments. From these findings, together with previous reports on the substrate specificity of the two enzymes in the V cycle, we propose that mutation to zeaxanthin epoxidase could have resulted in altered regulation and/or substrate specificity of the enzyme that gave rise to the parallel operation of two xanthophyll cycles in some plants. The distribution pattern of Lx in the mistletoe phylogeny inferred from 18S rRNA gene sequences also suggested that the occurrence of the Lx cycle is determined genetically. Possible molecular evolutionary processes that may have led to the operation of the Lx cycle in some mistletoes are discussed.

Carotenoids↗

PubMed2001

Quantitative determination of 13C-labeled and endogenous beta-carotene, lutein, and vitamin A in human plasma.

Quantitative procedures employing liquid-chromatography/particle beam-mass spectrometry (LC/PB-MS) and gas chromatography-mass spectrometry (GC-MS) were applied to the determination of the endogenous and 13C-labeled beta-carotene, lutein, and retinol in plasma of a subject who consumed kale (Brassica oleracea) that had been grown in a 13CO2-enriched atmosphere. All compounds were analyzed in the negative chemical ionization (NCI) mode using methane as the moderating reagent gas. Beta-carotene and lutein were analyzed using LC/PB-MS applying reversed-phase high-performance liquid chromatography (HPLC) separation procedures to resolve the analytes. The concentrations of the beta-carotene isotopomers in the plasma over a several-week period were determined using 2H8-beta-carotene as an internal standard. The total plasma concentrations of all trans-lutein were quantified by HPLC analysis with a photodiode array detector using beta-apo-8'-carotenal as an internal standard, and the ratio of the 13C:12C isotopomers of lutein was determined by PB-MS. The retinol isotopomers were collected from individual HPLC fractions of the plasma extract and then analyzed as the trimethylsilyl ethers by GC-MS in the NCI mode. The 13C- and 12C-retinol isotopomers were quantified using 2H4-retinol as an internal standard. These methods demonstrate the application of highly sensitive procedures employing NCI MS for the quantitative determination of carotenoids and vitamin A for the purpose of conducting metabolism studies of phytonutrients.

Brassica↗

PubMed1984

Effect of methyldopa on menopausal flushes, skin temperature, and luteinizing hormone secretion.

The effect of methyldopa (100 mg intravenously), the precursor of the alpha-receptor agonist alpha-methylnorepinephrine, on subjectively experienced menopausal flushes, skin temperature, and luteinizing hormone secretion was investigated in seven women in a double-blind, saline-controlled, crossover study. Subjects were monitored over a 3-hour period. Methyldopa significantly decreased the number of subjective flushes (p less than 0.05) and the number of cutaneous temperature peaks (p less than 0.05) but had no effect on the number of luteinizing hormone secretory pulses, variability of luteinizing hormone secretion, or total luteinizing hormone secretion. These studies indicate that alpha-adrenergic mechanisms (central and/or peripheral) play a role in the pathophysiology of menopausal flushes.

Climacteric↗

PubMed1989

Luteinizing hormone and ovulation timing in a therapeutic donor insemination program using frozen semen.

A series of 110 therapeutic donor insemination cycles was analyzed to determine the impact on fecundity when a urinary luteinizing hormone detection kit was used to plan inseminations. To prevent the transmission of human immunodeficiency virus, frozen semen, thawed after a 90-day quarantine, was used. The minimum standard for insemination with cryopreserved semen was a total of 24 x 10(6) motile sperm per milliliter after thawing. Fecundity was 0.12 when insemination timing was based on cervical mucus evaluation and basal body temperature charts and 0.13 when a urinary luteinizing hormone kit was also used to predict ovulation. Life table analysis with the log rank test showed no statistically significant difference in the number of cycles required to achieve conception between the group of patients using conventional methods of ovulation timing and the group of patients using the urinary luteinizing hormone kit. Urinary luteinizing hormone testing offers no advantage over conventional methods, such as cervical mucus examination and evaluation of basal body temperature, when ovulation is being timed for insemination with frozen donor semen.

Acquired Immunodeficiency Syndrome↗

PubMed1991

The gonadotropin-releasing hormone antagonist (Nal-Glu) acutely blocks the luteinizing hormone surge but allows for resumption of folliculogenesis in normal women.

The gonadotropin-releasing hormone antagonist offers several advantages over the use of the agonist and allows several physiologic questions to be addressed. In this study, we evaluated the ability of Nal-Glu to acutely inhibit the luteinizing hormone surge and prevent ovulation. We also assessed whether recovery of the follicle would be possible after several days of gonadotropin deprivation and estradiol decrement. Eight normal ovulatory women were randomized to control or Nal-Glu-treated cycles (50 micrograms/kg intramuscularly) for 3 to 4 days. Monitoring was carried out with daily vaginal ultrasonographic scans and serum estradiol levels and twice-daily serum luteinizing and follicle-stimulating hormone levels. Nal-Glu acutely inhibited the luteinizing hormone surge and ovulation, even when administered as late as the onset of the luteinizing hormone surge. Evidence was provided that spontaneous follicular rescue recurred in eight of 10 cycles after 3 to 4 days of Nal-Glu administration. Although an estradiol to follicular size dissociation occurred with Nal-Glu, subsequent ovulation occurred in 5.1 +/- 0.6 days after the last Nal-Glu dose. The decrement in estradiol after Nal-Glu administration correlated negatively with the days required for subsequent ovulation to occur (r = 0.77, p less than 0.05). The subsequent luteal phase also was normal in terms of length and progesterone levels. These data confirm the potency and efficacy of Nal-Glu in acutely inhibiting gonadotropins and extends our knowledge on the physiologic characteristics of the dominant follicle.

Adult↗

PubMed1993

Endogenous catecholamines augment the inhibitory effect of opioids on luteinizing hormone secretion during the midluteal phase.

OBJECTIVE: Our purpose was to test the hypothesis that endogenous catecholamines may interact with endogenous opioid peptides to influence gonadotropin secretion during the midluteal phase in normal women. STUDY DESIGN: Normal cycling women studied during the midluteal phase were randomized to one of four treatment groups: (1) alpha-methyl-para-tyrosine, (2) naloxone, (3) alpha-methyl-para-tyrosine and naloxone, and (4) control. Mean treatment luteinizing hormone levels were compared by analysis of variance. Pulse frequency, amplitude, and integrated area under the curve were assessed by CLUSTER analysis and compared by means of nonparametric analyses. RESULTS: Mean luteinizing hormone levels were significantly higher in the naloxone and alpha-methyl-para-tyrosine plus naloxone groups compared with alpha-methyl-para-tyrosine or placebo. Coadministration of alpha-methyl-para-tyrosine and naloxone caused a significant increase in large-burst luteinizing hormone pulses compared with the group receiving naloxone only. CONCLUSION: Endogenous catecholamines augment the inhibitory effect of opioids on luteinizing hormone secretion during the midluteal phase in normal cycling women.

Adolescent↗

PubMed1976

Effect of Ca2+, ruthenium red and ageing on pregnenolone production by mitochondrial fractions from normal and luteinizing hormone treated rat testes.

The effect of Ca2+ in vitro on pregnenolone production rates under various incubation conditions by mitochondrial fractions isolated from testes of normal rats and of rats after in vivo treatment with luteinizing hormone has been investigated. Concentrations of Ca2+ in the range of 0.1-0.5 mM stimulated succinate supported pregnenolone production in mitochondrial fractions from both control and luteinizing hormone treated testes. When mitochondrial fractions were isolated in 0.25 M sucrose without additions, Ca2+ in vitro increased succinate supported pregnenolone production rates in mitochondrial fractions isolated from control testes to a greater extent than in mitochondrial fractions, from luteinizing hormone treated testes. Production rates in control mitochondrial fraction, incubated in the presence of initial Ca2+ concentrations of 0.7 mM and higher were almost similar to production rates in relevant luteinizing hormone treated mitochondria.

Aging↗