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PubMed1990

Suppressive actions of a gonadotropin-releasing hormone antagonist on luteinizing hormone, follicle-stimulating hormone, and prolactin release in estrogen-deficient postmenopausal women.

We investigated time- and dose-dependent actions of a gonadotropin-releasing hormone antagonist, the "Nal-Glu" peptide [Ac-D2Nal1, 4CIDPhe2, D3Pal3, Arg5, DGlu6(AA), DAla10], in nine healthy estrogen-withdrawn postmenopausal women. Gonadotropin-releasing hormone antagonist was administered subcutaneously at doses of 10, 30, 100, and 300 micrograms/kg. Suppression of immunoactive luteinizing hormone concentrations was achieved with a 30 micrograms/kg dose of antagonist. Suppression of immunoactive follicle-stimulating hormone levels was less (40%) even at the highest antagonist dose (300 micrograms/kg). Bioactive luteinizing hormone concentrations also significantly decreased (greater than 60%) at the two antagonist doses tested (30 and 300 micrograms/kg). However, the lower antagonist dose showed an "escape" of bioactive luteinizing hormone values after 18 hours. No suppressive effects of the antagonist on prolactin secretion occurred at any dose tested. We conclude that this gonadotropin-releasing hormone antagonist can achieve effective, potent, and long-lasting suppression of pituitary secretion of biologically active luteinizing hormone at higher doses, but secretion of biologically active luteinizing hormone may "escape" at lower doses.

Aged↗

PubMed1995

Patterns of luteinizing and follicle-stimulating hormone pulsatility in menopausal women: correlation with plasma testosterone level and vasomotor instability episodes.

OBJECTIVE: The purpose of this study was to test the hypothesis that subtle differences among postmenopausal women can be detected by careful analysis of plasma luteinizing hormone and follicle-stimulating hormone pulses. STUDY DESIGN: Twelve postmenopausal women not receiving estrogen therapy were admitted for continuous blood withdrawal at the rate of 1 ml/min. Aliquots of 3 ml of pooled blood were collected every 3 minutes for 3 hours for the measurement of plasma luteinizing hormone and follicle-stimulating hormone. Estradiol, estrone, free testosterone, androstenedione, and dihydrotestosterone were measured from pooled specimens. Concomitantly, continuous recordings of peripheral blood flow and peripheral temperature from the opposite arm were obtained to detect vasomotor instability episodes. RESULTS: Analysis of gonadotropin pulses revealed a single pattern of plasma follicle-stimulating hormone but two distinct patterns of luteinizing hormone frequency and amplitude. One group of six women had a low mean (+/- SEM) interpulse interval frequency of 0.8 +/- 0.26 (p < 0.005) and a high mean amplitude of 18.4 +/- 1.8 IU/L (p < 0.05). The second group of six women had a high mean interpulse interval frequency of 3.5 +/- 0.34 and a low mean amplitude of 12.2 +/- 1.8 IU/L luteinizing hormone pulses. Women with this pattern had more inter-vasomotor instability episode intervals (3.5 +/- 1.6) than did women with low frequency and high amplitude (1.3 +/- 0.5, p < 0.001). Women with low frequency and high amplitude pulses had higher plasma levels of estrone (266 +/- 33 nmol/L), testosterone (2.3 +/- 0.7 mmol/L), and free testosterone (8.0 +/- 0.1 pmol/L, p < 0.05). CONCLUSION: There are subgroups of postmenopausal women with different patterns of luteinizing hormone pulsatility. This difference can be explained by higher steroid levels in women with low frequency and high amplitude pulses.

Androstenedione↗

PubMed1980

Regulation of ornithine decarboxylase activity by amino acids, cyclic AMP and luteinizing hormone in cultured mammalian cells.

Any one of five amino acis (alanine, asparagine, glutamine, glycine, and serine) is an essential requirement for the induction of ornithine decarboxylase (EC 4.1.1.17) in cultured chinese hamster ovary (CHO) cells maintained with a salts/glucose, medium. Each of these amino acids induced a striking activation of ornithine decarboxylase in the presence of dibutyryl cyclic AMP and luteinizing hormone. The effect of the other amino acids was considerably less or negligible. The active amino acids at optimal concentrations (10 mM) induced only a 10-20 fold enhancement of enzyme activity alone, while in the presence of dibutyryl cyclic AMP, ornithine decarboxylase activity was increased 40-50 fold within 7-8 h. Of the hormones and drugs tested, luteinizing hormone resulted in the highest (300-500 fold) induction of ornithine decarboxylase with optimal concentrations of dibutyryl cyclic AMP and asparagnine. Omission of dibutyryl cyclic AMP reduced this maximal activation to one half while optimal levels of luteinizing hormone alone caused no enhancement of ornithine decarboxylase activity. The induction of ornithine decarboxylase elicited by dibutyryl cyclic AMP, amino acid and luteinizing hormone was diminished about 50% with inhibitors of RNA and protein synthesis. The specific amino acid requirements for ornithine decarboxylase induction in chinese hamster ovary cells was similar to the requirements for induction in two other transformed cell lines. Understanding the mechanism of enzyme induction requires an identification of the essential components of the regulatory system. The essential requirement for enzyme induction is one of five amino acids. The induction of ornithine decarboxylase by dibutyryl cyclic AMP and luteinizing hormone was additive in the presence of an active amino acid.

Amino Acids↗

PubMed1993

Mode of action of prostaglandin F2 alpha in human luteinized granulosa cells: role of protein kinase C.

It is well documented that prostaglandin F2 alpha (PGF2 alpha) inhibits progesterone production in luteal cells, but its mode of action is uncertain. It has recently been suggested that PGF2 alpha acts by activating the calcium and phospholipid-dependent protein kinase, protein kinase C (PKC). This hypothesis has been tested by comparing the site and mode of action of PGF2 alpha, a PGF2 alpha analogue (cloprostenol) and the PKC activator phorbol myristate acetate (4 beta PMA) in human granulosa-lutein cells. PGF2 alpha and cloprostenol exerted similar concentration-dependent inhibitory actions on gonadotrophin-stimulated cyclic AMP (cAMP) accumulation and progesterone production by human granulosa-lutein cells. The similarity in the actions of PGF2 alpha and cloprostenol in human granulosa-lutein cells suggests that they can be used interchangeably to study the role of PGF2 alpha in the regulation of steroidogenesis in the human ovary. Gonadotrophin-stimulated cAMP accumulation and progesterone production was also concentration-dependently inhibited by 4 beta PMA. In addition, cloprostenol and 4 beta PMA also inhibited dibutyryl cAMP-stimulated progesterone production, suggesting that these compounds inhibit LH action at sites before and after the generation of cAMP. The pre-cAMP site of action can be localised to the stimulatory G-protein (Gs) as both compounds inhibited cholera toxin-stimulated cAMP accumulation without affecting forskolin-stimulated cAMP accumulation. The post cAMP site of action can be localised to actions on cholesterol side chain cleavage enzyme, as both cloprostenol and 4 beta PMA inhibited 22R hydroxycholesterol-supported progesterone production without affecting pregnenolone-supported progesterone production. The finding that cloprostenol and 4 beta PMA interact with the steroidogenic cascade in a similar manner is indicative of a shared common mediator of their actions in human granulosa-lutein cells, i.e. PKC. The inhibitory actions of PGF2 alpha and 4 beta PMA on hLH-stimulated progesterone production were abolished in the presence of the PKC inhibitor, staurosporine. In addition, in PKC-depleted cells (achieved by exposure to 4 beta PMA for 20 h) the inhibitory actions of PGF2 alpha and 4 beta PMA were abolished. These results support the hypothesis that the inhibitory actions of PGF2 alpha are mediated by PKC in human granulosa-lutein cells.

Bucladesine↗

PubMed1995

Isolation, structural elucidation, and partial synthesis of lutein dehydration products in extracts from human plasma.

All-E-(3R,6'R)-3-hydroxy-3',4'-didehydro-beta,gamma-carotene (anhydrolutein I) and all-E-(3R,6'R)-3-hydroxy-2',3'-didehydro-beta,epsilon-carotene (2',3'-anhydrolutein II) have been isolated and characterized from extracts of human plasma using semipreparative high-performance liquid chromatography (HPLC) on a C18 reversed-phase column. The identification of anhydroluteins was accomplished by comparison of the UV-Vis absorption and mass spectral data as well as HPLC-UV-Vis-mass spectrometry (MS) spiking experiments using fully characterized synthetic compounds. Partial synthesis of anhydroluteins from the reaction of lutein with 2% H2SO4 in acetone, in addition to anhydrolutein I (54%) and 2',3'-anhydrolutein II (19%), also gave (3'R)-3'-hydroxy-3,4-dehydro-beta-carotene (3',4'-anhydrolutein III, 19%). While anhydrolutein I has been shown to be usually accompanied by minute quantities of 2',3'-anhydrolutein II (ca. 7-10%) in human plasma, 3',4'-anhydrolutein III has not been detected. The presence of anhydrolutein I and II in human plasma is postulated to be due to acid catalyzed dehydration of the dietary lutein as it passes through the stomach. These anhydroluteins have also been prepared by conversion of lutein diacetate to the corresponding anhydrolutein acetates followed by alkaline hydrolysis. However, under identical acidic conditions, loss of acetic acid from lutein diacetate proceeded at a much slower rate than dehydration of lutein. The structures of the synthetic anhydroluteins, including their absolute configuration at C(3) and C(6') have been unambiguously established by 1H NMR and in part by 13C NMR, and circular dichroism.

Chromatography, High Pressure Liquid↗

PubMed2004

Deslorelin on Day 8 or 12 postovulation does not luteinize follicles during an artificially maintained diestrous phase in the mare.

Practical estrus synchronization schemes are needed for mares. The Ovsynch synchronization protocol for cattle involves the administration of gonadotropin-releasing hormone (GnRH) to induce ovulation or luteinization of dominant follicles during the luteal phase and prostaglandin 7 days later to cause regression of any luteal tissue and development of a preovulatory follicle. An Ovsynch-type synchronization program potentially could be developed for horses if luteinization or ovulation of diestrous follicles occurred in response to GnRH treatment. The objective of this study was to determine if administration of the GnRH agonist, deslorelin acetate, on Day 8 or 12 postovulation would induce luteinization or ovulation of diestrous follicles in the mare. The model used was cycling mares maintained in an artificial luteal phase by administration of a synthetic progestin following prostaglandin-induced luteal regression. On the day of ovulation, 21 light horse mares were randomly assigned to one of three groups: (1) no GnRH, altrenogest from Days 5 to 15 postovulation with prostaglandin on Day 15; (2) GnRH on Day 8, altrenogest from Days 5 to 15 with prostaglandin given on Day 6 to induce luteolysis of the primary corpus luteum, an implant containing 2.1mg of deslorelin acetate inserted on Day 8 and removed on Day 10, with a second prostaglandin treatment on Day 15; (3) GnRH on Day 12, altrenogest from Days 9 to 19, prostaglandin on Day 10, a deslorelin acetate implant injected on Day 12 (subsequently removed on Day 14), and a second dose of prostaglandin administered on Day 19. Follicular development was monitored every other day from Day 5 until a 30-mm sized follicle was observed, and then daily to detection of ovulation. Serum progesterone concentrations were determined daily for 12 consecutive days. Progesterone concentrations in Group 1 remained elevated until approximately Day 12 postovulation. Prostaglandin administration on Day 15 resulted in complete luteolysis in all seven mares. In Group 2, progesterone concentrations in six of seven mares declined to baseline after prostaglandin treatment. No increase in serum progesterone was noted in any of the six mares that were given GnRH on Day 8, including three mares that had diestrous follicles > or =30mm in diameter at the time of treatment. Similarly, progesterone concentrations in six of seven mares in Group 3 declined to baseline after prostaglandin and there was no increase in progesterone after administration of GnRH on Day 12. No ultrasound evidence of luteinization or ovulation of diestrous follicles were noted after GnRH administration in any mares of Group 2 or 3. In conclusion, administration of the GnRH agonist deslorelin acetate to mares failed to induce luteinization or ovulation of diestrous follicles. Consequently, the Ovsynch program (as used in cattle) has little efficacy for synchronization of estrus in mares.

Animals↗

PubMed2000

Management of women with polycystic ovary syndrome who experienced premature luteinization during clomiphene citrate treatment.

OBJECTIVE: To determine the preferred treatment modality in patients with PCOS who experienced premature luteinization during CC treatment. DESIGN: Prospective randomized study. SETTING: Tertiary medical center. PATIENTS: Twenty-two infertile women with PCOS demonstrating premature luteinization during at least two consecutive CC cycles. INTERVENTIONS: Randomized induction of ovulation either with FSH alone or with GnRH agonist combined with FSH for a single treatment cycle. MAIN OUTCOME MEASURES: Premature luteinization was defined as serum progesterone >1.5 ng/mL before hCG administration. RESULTS: Premature luteinization occurred in eight of the 10 patients (80%) in group A and in two of the 12 patients in group B (16.6%). This result corresponds to the higher mean (+/-SD) progesterone level present in group A patients as compared to those in group B (2.0 +/- 1.2 ng/mL vs. 1.2 +/- 0.6 ng/mL, P=0.03). No pregnancies were achieved in group A, whereas the pregnancy rate per cycle observed in group B was 33.3% (4/12). On the day of hCG administration, the maximum mean (+/-SD) estradiol level was significantly lower (P<0.0001) in group A (210.6 +/- 37.9 pg/mL) than in group B (600.3 +/- 253.8 pg/mL). The treatment duration and the number of FSH ampules used did not differ between the groups. CONCLUSIONS: Pituitary desensitization with GnRH analog in combination with FSH is superior to FSH-only treatment in PCOS patients who demonstrate premature luteinization during CC treatment.

Adult↗

PubMed1993

Effect of angiotensin II on human luteinized granulosa cells.

OBJECTIVE: To determine if human luteinized granulosa cells (GCs) exhibit angiotensin II (AII) receptors and if AII affects GC steroidogenesis. DESIGN: Luteinized GCs were either treated immediately or maintained in culture for up to 6 days before use. The presence of functional AII receptors was evaluated using the following criteria: [1] receptor binding of 125I-labeled AII; [2] changes in inositol phosphate production; [3] effects on progesterone (P) production; and [4] effects on cyclic adenosine 3':5' monophosphate (cAMP) production. RESULTS: No specific binding of 125I-labeled AII was observed using human luteinized GCs in culture. Angiotensin II did not alter the formation of [3H] inositol phosphates, nor did it alter the release of P from freshly isolated cells or cells that had been in culture for 5 days. Angiotensin II was also unable to alter basal or gonadotropin-stimulated cAMP production. These data suggest that human luteinized GCs exhibit little or no type 1 or type 2 AII receptors. CONCLUSION: This observation is in contrast to reports in rat granulosa that exhibit AII receptors. The reason for a lack of AII receptor expression on human luteinized GCs is unknown but could be because of luteal phase down regulation with gonadotropin-releasing hormone agonist or the subsequent stimulation with gonadotropins in these women before follicular stimulation.

Angiotensin II↗

PubMed1995

Relationship between circulating human chorionic gonadotropin levels and premature luteinization in cycles of controlled ovarian hyperstimulation.

OBJECTIVE: To determine if premature luteinization (serum P levels > 1.1 ng/mL on or before the day of hCG administration) during controlled ovarian hyperstimulation (COH) is associated with elevated levels of serum hCG. SETTING: Tertiary fertility center. DESIGN: Retrospective evaluation of ovum donors undergoing COH. PATIENTS: Forty-four women underwent COH. Comparisons of serum hCG levels and hormonal and cycle characteristics were made between cycles with premature luteinization (group I) and without premature luteinization (group II). RESULTS: Group I (16 women) were similar to women in group II in age, amount of hMG, and the ratio of FSH:hMG received. Both groups received hCG on similar days, but women in group I had higher peak E2 levels. Serum hCG levels increased and correlated with serum P levels in group I only and were higher on the day of hCG administration (group I 1.8 +/- 0.9 mIU/mL versus group II 1.2 +/- 0.45 mIU/mL; conversion factor to SI unit, 1.00). Peak E2 and LH levels, ampules of hMG and the FSH:LH ratio, and day of hCG administration did not correlate with hCG levels. Human chorionic gonadotropin exposure, as measured by area under the curve, was significantly higher in group I compared with group II. CONCLUSION: Higher serum levels of hCG and integrated hCG exposure are found in COH cycles with premature luteinization compared with cycles without premature luteinization. Higher hCG levels may be due to decreased clearance of hCG from the circulation and/or the hCG content of hMG.

Adult↗

PubMed1999

Beta-carotene and lycopene, but not lutein, supplementation changes the plasma fatty acid profile of healthy male non-smokers.

Polyunsaturated fatty acids (PUFAs) are highly susceptible to free radical attack. In vitro studies of carotenoids--including beta-carotene, lycopene, and lutein--have shown them to be effective quenchers of singlet oxygen, to have good radical-trapping properties, or to be effective peroxyl radical scavengers (or to have a combination of these qualities). If carotenoids act as antioxidants in vivo, then arguably, plasma PUFA should be conserved. The objective of the current study was to answer the question "Does supplementation with beta-carotene, lycopene, or lutein, at dietarily achievable levels, over a time period known to significantly increase circulating carote concentrations, lead to an observable increase in fasting plasma PUFA?" The normal diets of human volunteers were supplemented with either 15 mg/day beta-carotene (n = 25), lycopene (n = 23), or lutein (n = 21) for 26 days in three independent double-blind, placebo-controlled supplementation studies. Supplementation with beta-carotene increased plasma linoleic acid but left the polyunsaturated:saturated (P:S) fatty acid ratio unaltered. In contrast, supplementation with lycopene reduced linoleic acid, which resulted in a large decrease in the P:S ratio. Lutein supplementation had no effect. It was concluded that neither beta-carotene, lycopene, nor lutein supplementation engender antioxidant effects that lead to the widespread general conservation of plasma PUFAs. Beta-carotene and lycopene supplementation appear to interact with the metabolism of linoleic acid, the "essential" fatty acid, resulting in either an increase (beta-carotene) or decrease (lycopene) in its plasma concentration. Alterations in plasma 18:2 or P:S ratios could ultimately lead to changes in tissue cellular membrane composition and hence to alterations in membrane fluidity and cell-surface protein expression.

Adolescent↗

PubMed2001

Lutein production by Muriellopsis sp. in an outdoor tubular photobioreactor.

The effect of dilution rate, mixing and daily solar cycles on lutein and biomass productivity of the green unicellular alga Muriellopsis sp. has been studied, throughout the year, in an outdoor tubular photobioreactor. Highest productivity values, for both lutein (about 180 mg m(-2) per day) and biomass (about 40 g (dry weight) m(-2) per day) were achieved on May and July. Values for the optimal dilution rate varied, being lower in May (0.06 h(-1)) than in November (0.09 h(-1)). Similar values for photosynthetic efficiency (about 4%) were recorded throughout the year, indicating that optimization of culture conditions was achieved for each experimental period. Along the daily solar cycle, there was a fast increase of lutein content of Muriellopsis sp. in response to irradiance during the early hours of daytime, with maximal lutein content (about 6 mg (g dry weight)(-1)) being recorded at noon, and decreasing slowly, thereafter. An increase in cell growth was observed following the establishment of maximum lutein/chlorophyll ratio, which might indicate a role for lutein in protecting cells from photodamage.

Biomass↗

PubMed2004

Improved separation method for highly purified lutein from Chlorella powder using jet mill and flash column chromatography on silica gel.

We investigated an improved method for the separation of high-purified lutein from a commercially available spray-dried Chlorella powder (CP) using fine grinding by jet mill and flash column chromatography on a silica gel. Saponification and extraction of lutein were enhanced 2.3-2.9-fold in jet mill-treated CP (mean particle size, 20 microm) as compared to untreated CP (mean particle size, 67 microm). The carotenoid extract was dissolved in ether-hexane (1:1 v/v) and subjected to flash column chromatography on silica gel. A mixture of alpha- and beta-carotene was eluted with hexane, followed by elution with hexane-acetone-chloroform (7:2:1 v/v). Lutein (dark-orange band) was collected after the elution of an unknown colorless compound (detected based on UV absorbance). The purity of lutein in this fraction was over 99%, and the yield was 60%. The present study provides key information for obtaining highly purified lutein using flash column chromatography on a silica gel.

Chlorella↗

PubMed2005

Ultrafast excitation relaxation dynamics of lutein in solution and in the light-harvesting complexes II isolated from Arabidopsis thaliana.

Ultrafast excitation relaxation dynamics and energy-transfer processes in the light-harvesting complex II (LHC II) of Arabidopsis thaliana were examined at physiological temperature using femtosecond time-resolved fluorescence spectroscopy. Energy transfer from lutein to Chl a proceeded with a rate constant of k(ET) = 1.8-1.9 x 10(13) s(-1) and a yield of approximately Phi(ET) = 0.70, whereas that from neoxanthin to Chl a had a rate constant of k(ET) = 6.5 x 10(11) s(-1) and a yield at the most of Phi(ET) = 0.09. Fluorescence anisotropic decay of lutein in LHC II showed a value larger than 0.4 at the initial state and decayed to approximately 0.1 in 0.3 ps, indicating that two lutein molecules interact with each other in LHC II. In solution, anisotropy of lutein remained constant (0.38) independent of time, and thus a new excited state inferred between the S(2) (1B(u)) state and the S(1) (2A(g)) state was not applicable for lutein in solution. Energy migration processes among Chl a or Chl b molecules were clearly resolved by kinetic analysis. On the basis of these results, relaxation processes and energy-transfer kinetics in LHC II of A. thaliana are discussed.

Arabidopsis↗

PubMed2001

Supplementation of rats with a lutein mixture preserved with vitamin E reduces tissue phylloquinone and menaquinone-4.

The modulation of tissue concentrations of vitamin K by a lutein supplement preserved with natural vitamin E was studied in Fischer 344 rats. Vitamin K is necessary for blood coagulation and may be essential for tissue and bone health. Weanling male rats were fed the AIN-93G diet (control) or modified AIN-93G diets containing 0.3, 0.6, 1.2, 2.4 and 4.8 g supplement/100 g diet for 8 weeks. The supplement contained 5% lutein, 0.22% zeaxanthin and 2.2% natural vitamin E as a preservative. Concentrations of trans-phylloquinone in the plasma (nmol/mmol triglycerides) and heart were significantly reduced (P < or = 0.05) in rats fed the supplement. The reductions in trans-phylloquinone in the heart ranged from approximately 20 to 60% of the control. Concentrations of phylloquinone in the liver were significantly lower in the rats fed the supplement at levels > or = 1.2 g/100 g diet than in the control rats. Ratios of cis/trans phylloquinone in liver and heart increased and concentrations of menaquinone-4 in heart decreased as the dietary level of the lutein supplement increased. The results suggest that the lutein supplement affected the absorption, tissue uptake and/or turnover rate of vitamin K. The presence of other components in the supplement confounded the interpretation of the biological effects of lutein alone on vitamin K metabolism.

Animal Feed↗

PubMed1976

Correlation of protein kinase activation and testosterone production after stimulation of Leydig cells with luteinizing hormone.

The effect of different doses of luteinizing hormone on activation of protein kinases, cyclic AMP and testosterone production was studied in purified rat testis Leydig-cell preparations in the presence of 3-isobutyl-1-methylxanthine (a phosphodiesterase inhibitor). In addition, the nature of the protein kinases present in these cells and other tissues was investigated. The following results were obtained. 1. With all the amounts of luteinizing hormone used (0.1-1000 ng/ml), both activation of protein kinase and stimulation of testosterone production were demonstrated. With the lowest amount of luteinizing hormone (0.1 ng/ml), an 8.4+/-0.9% (S.E.M.,n=6) stimulation of protein kinase activation occurred, increasing to 100% with 1000 ng/ml, compared with 3.2+/-1.0%(S.E.M.,n=7) and 100% stimulation of testosterone production with 0.1 and 100 ng/ml respectively. 2. With amounts of luteinizing hormone up to 1 ng/ml (which gave half-maximal stimulation of testosterone production) no detectable increases in net cyclic AMP production were obtained. With higher amounts of luteinizing hormone, cyclic AMP production increased, but maximal production was not reached with 1000 ng/ml. 3. Two isoenzymic forms of protein kinase were present in Leydig cells and seminiferous tubules; type I was eluted with 0.075 M-and type II with 0.22-0.25 m-NaCl from DEAE-cellulose columns. 4. The protein kinase activity was not affected by the presence of erythrocytes in the Leydig-cell preparation, but varied depending on the type of histone used as substrate (histone F2b greater than mixed greater than histone F1).

Animals↗

PubMed1975

Restoration of normal pituitary gonadotropin reserve by administration of luteinizing-hormone-releasing hormone in patients with hypogonadotropic hypogonadism.

To elucidate whether diminished pituitary gonadotropin reserve can be restored by repeated stimulation with luteinizing-hormone-releasing hormone, plasma luteinizing hormone and follicly-stimulating hormone responses were studied before and after daily intravenous infusion of 400 mug of luteinizing-hormone-releasing hormone for two to 23 days, in patients with hypogonadotropic hypogonadism of various causes. In five of nine patients with isolated gonadotropin deficiency, the impaired plasma luteinizing hormone response was restored to normal after treatment for seven days or more, whereas it was unchanged in four patients treated for less than five days. However, six patients with anorexia nervosa regained normal responses after three to five days' treatment. Five of nine patients with organic hypothalamopituitary lesions also showed normal responsiveness after five to seven days' treatment. These results suggest that the response to the test after repeated administration of luteinizing-hormone-releasing hormone is of value for the diagnosis of hypogonadism of hypothalamic origin.

Adolescent↗

PubMed1983

A chronobiologic abnormality in luteinizing hormone secretion in teenage girls with the polycystic-ovary syndrome.

We investigated possible abnormalities of central-nervous-system regulation of luteinizing hormone secretion in the polycystic-ovary syndrome by determining the plasma concentrations of luteinizing hormone over a 24-hour period in five teenage girls with the syndrome; profiles of prolactin and cortisol were also obtained. Four of the five patients had strikingly abnormal plasma luteinizing hormone profiles: whereas normal pubertal girls have a daily surge in secretion of luteinizing hormone that is coterminous with their nocturnal sleep period, our patients had surges that were grossly desynchronized from their sleep period, occurring seven to eight hours later in the daytime than normal. The chronobiologic disturbance involved only luteinizing hormone; the profiles of cortisol and prolactin were normal. This finding points to the central nervous system as the probable locus of the initiating pathophysiology of polycystic-ovary syndrome.

Adolescent↗

PubMed2006

Defining the primary route for lutein synthesis in plants: the role of Arabidopsis carotenoid beta-ring hydroxylase CYP97A3.

Lutein, a dihydroxy derivative of alpha-carotene (beta,epsilon-carotene), is the most abundant carotenoid in photosynthetic plant tissues where it plays important roles in light-harvesting complex-II structure and function. The synthesis of lutein from lycopene requires at least four distinct enzymatic reactions: beta- and epsilon-ring cyclizations and hydroxylation of each ring at the C-3 position. Three carotenoid hydroxylases have already been identified in Arabidopsis, two nonheme diiron beta-ring monooxygenases (the B1 and B2 loci) that primarily catalyze hydroxylation of the beta-ring of beta,beta-carotenoids and one heme-containing monooxygenase (CYP97C1, the LUT1 locus) that catalyzes hydroxylation of the epsilon-ring of beta,epsilon-carotenoids. In this study, we demonstrate that Arabidopsis CYP97A3 (the LUT5 locus) encodes a fourth carotenoid hydroxylase with major in vivo activity toward the beta-ring of alpha-carotene (beta,epsilon-carotene) and minor activity on the beta-rings of beta-carotene (beta,beta-carotene). A cyp97a3-null allele, lut5-1, causes an accumulation of alpha-carotene at a level equivalent to beta-carotene in wild type, which is stably incorporated into photosystems, and a 35% reduction in beta-carotene-derived xanthophylls. That lut5-1 still produces 80% of wild-type lutein levels, indicating at least one of the other carotene hydroxylases, can partially compensate for the loss of CYP97A3 activity. From these data, we propose a model for the preferred pathway for lutein synthesis in plants: ring cyclizations to form alpha-carotene, beta-ring hydroxylation of alpha-carotene by CYP97A3 to produce zeinoxanthin, followed by epsilon-ring hydroxylation of zeinoxanthin by CYP97C1 to produce lutein.

Arabidopsis↗