Study of the linear conversion of lower hybrid waves in the FT-1 tokamak by the enhanced time-of-flight scattering technique

The propagation of lower hybrid (LH) waves in a tokamak plasma in the presence of an LH resonance surface is studied experimentally with the use of a specially elaborated technique based on the backscattering of the probing microwave radiation in the upper hybrid resonance region. The technique provides resolution in the wave vectors of the scattering density fluctuations. The conditions are determined under which the LH wave propagates in accordance with the predictions of linear theory and is converted into the short-wave-length ion Bernstein mode. The parameter range is found in which the predictions of linear theory fail to hold and the nonlinear effects come into play during LH wave conversion. The radial wavelengths of the LH and ion Bernstein waves are determined.     

Role of LH pulse amplitude and the rate of LH increase on oestradiol-17 beta secretion by immature rat ovaries in perfusion culture

Immature rat ovaries were placed in perifusion culture and exposed to LH in a variety of patterns, while tonic levels of FSH (200 ng/ml) were maintained. Perifusate was collected every 5 min and assayed for oestradiol-17 beta. In Exp. I, LH was delivered at 50 ng/ml for 30 min then reduced to 0 ng/ml for an additional 30 min (50 ng/ml LH step) or as linear increasing concentrations reaching 50 ng/ml by 30 min of culture then linear decreasing concentrations reaching 0 ng/ml by 30 min of culture (50 ng/ml LH ramp). Although both delivery systems exposed the tissue to 250 ng LH over the 1-h culture period, only the 50 ng/ml step significantly increased oestradiol-17 beta secretion rates (P less than 0.05). In Exp. II, ovaries were not exposed to LH for the first 30 min of culture but then LH was administered at a concentration of 25 or 50 ng/ml for 30 min. The LH concentration was reduced to 0 ng/ml for an additional 30 min of culture. Oestradiol-17 beta secretion rates were increased 50% by both treatments. These results suggest that the mechanism by which an LH pulse stimulates the immature ovary to secrete oestradiol-17 beta is, in part (1) 'threshold'-dependent and not solely dependent on the amount of LH administered, and (2) dependent on the time required to achieve a 'threshold' level.     

Measurement of messenger RNA for luteinizing hormone beta-subunit and alpha-subunit during gestation and the postpartum period in ewes

Pituitary content of luteinizing hormone (LH) and mRNAs for LH beta-subunit (LH beta), alpha-subunit, prolactin, and growth hormone were measured in ewes on Days 50 and 140 of gestation and on Days 2, 13, 22, and 35 postpartum. Content of LH in dissociated anterior pituitary cells declined (P less than 0.05) between Days 50 and 140 of gestation and remained low at 2 days postpartum. By 22 days postpartum, pituitary concentrations of LH were comparable to concentrations in normally cycling ewes. During gestation concentrations of mRNA for LH beta and alpha-subunit paralleled changes in cellular content of LH, reaching minimal levels on Day 140. By Day 2 postpartum, pituitary concentrations of mRNAs for LH beta and alpha-subunit began to increase; they reached maximum levels by Day 13 postpartum. There appeared to be a gradual linear increase in mRNA for prolactin through gestation and the postpartum period. No changes in mRNA for growth hormone were noted during the prepartum or postpartum periods. These data suggest that the decline in pituitary concentrations of LH during gestation is due to a decrease in cellular mRNA for LH beta and alpha-subunit. The increase in mRNA for LH beta and alpha-subunit appears to precede an increase in cellular content of LH in the postpartum ewe by several days.     

Plasma luteinizing hormone during pregnancy in the pig

Three chronically catheterized Duroc gilts were used to characterize the pattern of plasma LH in the systemic circulation during pregnancy. Blood samples were collected four times daily (08.00, 12.00, 16.00 and 20.00 h) from the second day of estrus until day 7 postpartum in one pig and to 108 and 98 days of gestation in the remaining two. The concentration of plasma LH fluctuated in a pulsatile manner throughout the studied periods of gestation in all three pigs, with decreasing amplitude towards parturition. Significant correlations between the decline of LH levels and the day of pregnancy were found, and the equations for the linear regression lines are presented. It is suggested that the level of LH in early and mid-pregnancy mimics LH concentrations in the midluteal phase of the estrous cycle.     

Release of lutropin (LH) and follitropin (FSH) in cattle after administration of a new gonadoliberin (GnRH) analogue in comparison with the gonadoliberin decapeptide.

A gonadoliberin (GnRH) analogue nonapeptide (Hoe 766) was administered intramuscularly in concentrations between 2.5 and 50 μg to m?ture cows in order to study the response of lutropin (LH) and follitropin (FSH). Results were compared with those from experiments of the GnRH decapeptide (Hoe 471). Plasma LH and FSH were radio-immunologically determined. Increasing doses of GnRH analogue up to 15–20 μg caused an approximately linear increase in total plasma LH and FSH until the response reached a plateau. With these amounts peak values were about 60 fold higher for LH and 3.5 fold higher for FSH than basal levels about 135 minutes after injection. Higher values lasted for more than 6 h for LH and about 5 h for FSH. The LH response was much greater and more prolonged than for FSH.Doses of the nonapeptide analogue 50 to 70 times lower than the GnRH decapeptide provoked about the same height and duration of LH and FSH response.     

Identification of two distinct structural motifs that, when added to the C-terminal tail of the rat LH receptor, redirect the internalized hormone-receptor complex from a degradation to a recycling pathway

We show that most of the internalized rat LH receptor is routed to a lysosomal degradation pathway whereas a substantial portion of the human LH receptor is routed to a recycling pathway. Chimeras of these two receptors identified a linear amino acid sequence (GTALL) present near the C terminus of the human LH receptor that, when grafted onto the rat LH receptor, redirects most of the rat LH receptor to a recycling pathway. Removal of the GTALL sequence from the human LH receptor failed to affect its routing, however. The GTALL sequence shows homology with the C-terminal tetrapeptide (DSLL) of the beta2-adrenergic receptor, a motif that has been reported to mediate the recycling of the internalized beta2-adrenergic receptor by binding to ezrin-radixin-moesin-binding phosphoprotein-50. Addition of the DSLL tetrapeptide to the C terminus of the rat LH receptor also redirects most of the internalized rat LH receptor to a recycling pathway but, like the recycling of the human LH receptor, this rerouting is not mediated by ezrin-radixin-moesin-binding phosphoprotein-50. We conclude that most of the internalized rat LH receptor is degraded because its C-terminal tail lacks motifs that promote recycling and that two distinct, but homologous, motifs (DSLL at the C terminus or GTALL near the C terminus) can reroute the internalized rat LH receptor to a recycling pathway that is independent of ezrin-radixin-moesin-binding phosphoprotein-50.     

Characterization of equine luteinizing hormone by chromatofocusing

Three equine luteinizing hormone (LH) preparations (eLH-A, -B, and -C) recently have been isolated in our laboratory and were shown to differ in average basicity (eLH-A greater than -B greater than -C). The present study further characterizes these preparations by chromatofocusing. Each of these preparations are comprised of a family of isohormones, with 5 major immunoreactive peaks in the pH range of 7 to 4 (approx. pIs = 6.6, 6.1, 5.7, 5.2, and 4.8), with varying amounts of material eluting to either side of the pH gradient. Although similar isoforms are seen in all three LH preparations, the relative proportions of different isoforms vary in a manner reflecting the average charge properties of eLH-A, -B, and -C. While eLH-A contains predominantly basic forms, eLH-C consists largely of acidic material, and eLH-B is composed mostly of isohormones with pIs intermediate to eLH-A and -C. Chromatofocusing of a crude extract from a single horse pituitary gland revealed isohormone peaks corresponding to those found in the highly purified LH preparations. Peak fractions of the various isoforms were used to generate a variety of activity ratios (LH bioactivity:LH radioimmunoassay (RIA), LH radioreceptorassay (RRA):LH RIA, LH bioactivity:LH RRA, follicle-stimulating hormone (FSH) RRA:LH RIA, and FSH RRA:LH RRA activity ratios). The LH bioactivity:LH receptor binding potency ratio showed a linear increase with increasing isohormone acidity (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Bovine cumulus/oocyte complex: quantification of LH/hCG receptors

LH/hCG receptors of the bovine cumulus/oocyte complex were quantified, and their maximum binding capacities and affinity constants were determined by Scatchard analysis. Specific binding of these gonadotropins to receptors in follicles of different sizes was also determined by radiolabeling techniques. A greater number of receptors was observed to be bound to LH than to hCG (P < 0.05); however, affinity constants did not significantly differ (P > 0.05). The results of specific binding of the gonadotropins presented differences in relation to follicle size. Differences in the specific binding values of LH and hCG were verified (P < 0.05), but when submitted to linear regression analysis, presented similar behaviors in relation to follicle size. It is concluded that receptors of bovine cumulus/oocyte complex cells bind specifically to LH/hCG, that binding capacity is inversely proportional to follicle size, and that the behavior of hCG is similar to that of LH, suggesting that hCG can also promote the maturation of bovine oocytes when used in concentrations greater than LH.     

Effect of nembutal on LH release in baboons.

Regularly cycling female baboons were selected and maintained under a diurnal light schedule from 0500 to 1900 hr (CST). Beginning three days prior to the expected LH peak, blood was collected daily at 0800 and 1600 hr for 6 days in 5 baboons under light sedation for radioimmunoassay of plasma LH and estrogen. The plasma level of LH increased linearly and reached a peak in the afternoon of the second day. The peak in plasma estrogen appeared prior to the LH peak. In order to examine the critical period of LH surge in baboons, nembutal was injected daily at 1300 hr beginning a few days prior to expected LH relase. Initial dose of nembutal was 35 mg/kg body weight, but a supplementary dose was later required for a full 5 hours of anesthesia. Blood was collected at 1600 hr from 4 baboons during nembutal injections and after cessation of nembutal injections for radioimmunoassay of plasma LH and estrogen. It was found that nembutal injections suppressed LH release in 2 baboons, and caused a delay of LH release in 2 baboons. However, the plasma level of estrogen declined immediately after initiation of nembutal injection and remained lower. The evidence illustrates the nature of the neural components of LH release which became effective in the afternoon during the ovulatory phase. In addition, a linear increase in plasma level of LH, which is due to accumulation of circulating LH, is necessary for induction of ovulation in baboons.     

介绍一种LHRH调节LH分泌的离体模型—分散垂体细胞灌流技术

成年雄性 SD 大鼠断头后分离出垂体前叶(anterior pituitary,AP)。用胰蛋白酶消化和机械分散制备 AP 细胞(成活率大于95%)。分散的细胞悬液与生物凝胶混合后装上灌流柱,然后用 M199溶液连续灌流24h 以上。每间隔1~h 给予一次6min 的 LHRH 脉冲式刺激。细胞在此灌流过程中有一个稳定的基础 LH 分泌水平。LHRH 刺激能迅速引起 LH 分泌。对同一剂量 LHRH 的多次刺激可产生相同的 LH 脉冲。在一定的 LHRH 浓度范围内(1×10~(-10)_1×10~(-7)mol/L),LH 分泌与 LHRH 的剂量-效应曲线呈线性。实验结果表明,连续灌流分散的 AP 细胞的技术,优于单层细胞培养和组织块灌流等其他方法,是一种较为理想的研究LHRH 调节 LH 分泌机理的体外模型。     

Controlling interrelationships of progesterone/LH and estradiol/LH in mares

The interrelationships of progesterone, estradiol, and LH were studied in mares (n=9), beginning at the first ovulation (Day 0) of an interovulatory interval. An increase in mean progesterone concentrations began on Day 0 and reached maximum on Day 6, with luteolysis beginning on Day 14. A common progesterone threshold concentration of about 2 ng/ml for a negative effect on LH occurred at the beginning and end of the luteal phase. Progesterone and LH concentrations decreased at a similar rate from Day 6 until the onset of luteolysis on Day 14, consistent with a decreasing positive effect of LH on progesterone. Concentrations of LH during the increase in the ovulatory surge consisted of two linear regression segments involving a rate of 0.4 ng/ml/day for Days 14-22 and 1.8 ng/ml/day for Day 22 to 1 day after the second ovulation. The end of the first segment and beginning of the second segment was 2 days before ovulation and was the day the ovulatory estradiol surge was at a peak.     

Further evidence that prolactin does not affect gonadotropin release at pituitary level

In a primary monolayer cell culture of the anterior pituitary from mature male rats the effects of exogenous rPrl (rPrl exog.) and endogenously secreted rPrl (rPrl endog.) on basal and LHRH stimulated LH secretion were investigated. In pilot studies basal Prl- and LH secretion as well as influence of various LHRH concentrations (10(-1)-10(+3) ng/ml) on Prl- and LH release were observed. The influence of exogenous rPrl was studied at various concentrations (50-500 ng/ml) and with preincubation periods of 2 hrs and 6 hrs before starting LHRH stimulation. The dopamine agonist bromocriptine and the dopamine antagonist sulpirid were preferentially used to prove physiologic function of the cell system presented. Basal LH secretion started after a delay of 3 hrs, whereas basal Prl secretion began immediately showing a linear rise for 9 hrs. LHRH stimulation resulted in a non-linear dose and time dependent LH secretion. LHRH showed no influence on endogenous Prl (rPrl endog.) secretion of the mammotroph cells. Exogenous Prl (rPrl exog.) did not affect spontaneous Prl release excluding ultra short loop inhibition in this cell system. Furthermore, exogenous Prl had no effect on either basal or LHRH stimulated LH secretion even after a preincubation period of up to 6 hrs and at concentrations generally observed for prolactin secreting tumors. Bromocriptine suppressed endogenous Prl release and did not affect LH secretion. Sulpirid had no influence on either Prl or LH secretion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Inappropriate gonadotropin secretion in the polycystic ovary syndrome

In this study was investigated the diagnostic significance of double stimulation test with (that is of 25 micrograms rapid injection intravenously twice at an interval of 120 minutes and the misure of maximal net increment of serum LH after the first GnRH injection expressed as delta 1 and after the second injection, expressed as delta 2) to discriminate patients with idiopatic hirsutism. This test was effectuated on 8 patients with PCO (presence of polycystic ovaries on Ecografya and/or Laparoscopy) and 8 patients with idiopatic hirsutism (presence of normal morphology ovaries). Basal LH, FSH, E1, E2 and delta 4 levels were also measured. The value of LH delta 2 were more elevated in patients with PCO (p less than 0,0002) than the patients with idiopatic hirsutism. Consequently it as been value of LH delta 2 to discriminate the two different groups of patients. In PCO patients were also found: -a positive linear correlation between LH delta 1 and basal concentration serum of E2 (p less than 0,001); -a significant increase of basal levels serum of delta 4 (p less than 0,02); while the values of basal LH and LH delta 1 were found superior only on 4 of the initial 8 patients, the basal values of E1 and E2 were at the superior found of the norm and basal FSH, FSH delta 1 and FSH delta 2 values were found normals.     

Variation in supramolecular organisation of the photosynthetic membrane of Rhodobacter sphaeroides induced by alteration of PufX

In purple bacteria of the genus Rhodobacter (Rba.), an LH1 antenna complex surrounds the photochemical reaction centre (RC) with a PufX protein preventing the LH1 complex from completely encircling the RC. In membranes of Rba. sphaeroides, RC–LH1 complexes associate as dimers which in turn assemble into longer range ordered arrays. The present work uses linear dichroism (LD) and dark-minus-light difference LD (ΔLD) to probe the organisation of genetically altered RC–LH1 complexes in intact membranes. The data support previous proposals that Rba. capsulatus, and Rba. sphaeroides heterologously expressing the PufX protein from Rba. capsulatus, produce monomeric core complexes in membranes that lack long-range order. Similarly, Rba. sphaeroides with a point mutation in the Gly 51 residue of PufX, which is located on the membrane-periplasm interface, assembles mainly non-ordered RC–LH1 complexes that are most likely monomeric. All the Rba. sphaeroides membranes in their ΔLD spectra exhibited a spectral fingerprint of small degree of organisation implying the possibility of ordering influence of LH1, and leading to an important conclusion that PufX itself has no influence on ordering RC–LH1 complexes, as long-range order appears to be induced only through its role of configuring RC–LH1 complexes into dimers.     

Conjugation-length dependence of the T1 lifetimes of carotenoids free in solution and incorporated into the LH2, LH1, RC, and RC-LH1 complexes: possible mechanisms of triplet-energy dissipation

In addition to the roles of antioxidant and spacer, carotenoids (Cars) in purple photosynthetic bacteria pursue two physiological functions, i.e., light harvesting and photoprotection. To reveal the mechanisms of the photoprotective function, i.e., quenching triplet bacteriochlorophyll to prevent the sensitized generation of singlet oxygen, the triplet absorption spectra were recorded for Cars, where the number of conjugated double bonds (n) is in the region of 9-13, to determine the dependence on n of the triplet lifetime. The Cars examined include those in (a) solution; (b) the reconstituted LH1 complexes; (c) the native LH2 complexes from Rba. sphaeroides G1C, Rba. sphaeroides 2.4.1, Rsp. molischianum, and Rps. acidophila 10050; (d) the RCs from Rba. sphaeroides G1C, Rba. sphaeroides 2.4.1, and Rsp. rubrum S1; and (e) the RC-LH1 complexes from Rba. sphaeroides G1C, Rba. sphaeroides 2.4.1, Rsp. molischianum, Rps. acidophila 10050, and Rsp. rubrum S1. The results lead us to propose the following mechanisms: (i) A substantial shift of the linear dependence to shorter lifetimes on going from solution to the LH2 complex was ascribed to the twisting of the Car conjugated chain. (ii) A substantial decrease in the slope of the linear dependence on going from the reconstituted LH1 to the LH1 component of the RC-LH1 complex was ascribed to the minor-component Car forming a leak channel of triplet energy. (iii) The loss of conjugation-length dependence on going from the isolated RC to the RC component of the RC-LH1 complex was ascribed to the presence of a triplet-energy reservoir consisting of bacteriochlorophylls in the RC component.     

Circulating gonadotrophins during a period of restricted energy intake in relation to body condition in heifers.

Beef heifers, 13 months old, were fed to achieve high (7.6 +/- 0.2 units) or low (3.9 +/- 0.1 units) body condition by feeding them one of two diets for 20 weeks. During week 17 of the growth phase, all heifers were ovariectomized. From week 20 to week 27 (restriction phase), all heifers were fed a daily diet containing 0.071 MJ metabolizable energy kg-1 body weight. At weekly intervals throughout the restriction phase, blood samples were collected at 10-min intervals for 11 h to determine the pattern of secretion of luteinizing hormone (LH), the amount of LH released in response to 750 ng (pituitary responsiveness) and 50 micrograms LH-releasing hormone (LHRH, releasable stores) and mean concentrations of follicle-stimulating hormone (FSH) in the circulation. Body weight declined during the restriction phase in a similar fashion in heifers with high and low body condition and changes in body weight were unrelated to mean concentrations of LH and FSH and frequency of LH pulses. Amplitude of LH pulses and responsiveness to 750 ng LHRH increased in a linear fashion with weight loss in heifers with low but not in those with high body condition. The amount of LH released in response to 50 micrograms LHRH decreased with increasing weight loss in heifers with high but not with low body condition, indicating that releasable pools of LH declined with increased weight loss in heifers with high body condition.(ABSTRACT TRUNCATED AT 250 WORDS)     

Differential regulation of preovulatory luteinizing hormone and follicle-stimulating hormone release by opioids in the proestrous rat

We have investigated the role of mu- and kappa-opioid receptors in the central control of preovulatory LH and FSH release in the proestrous rat. Animals were anesthetized with chloral hydrate at 14:00 h on proestrus day. Following femoral artery cannulation, they were mounted in a stereotaxic apparatus. Morphine and U-50488H (benzene-acetamide methane sulphonate) were infused intracerebroventricularly either alone or in combination with naloxone and MR1452, respectively. Controls received sterile saline alone. Blood samples were obtained at hourly intervals between 15:00 h and 17:00 h. Plasma LH and FSH levels were measured by radioimmunoassay. Morphine did not significantly change plasma LH levels at 15:00 h and 16:00 h sampling intervals. A significant increase was observed at 17:00 h compared to the controls (p<0.05). U-50488H significantly increased LH levels at 16:00 h and 17:00 h (p<0.05). The co-administration of naloxone and MR1452 with mu- and kappa-agonist had no significant effect on LH levels at any sampling interval. In all groups, LH levels showed a linear rise over the sampling period between 15:00 h and 17:00 h. None of the treatments significantly altered plasma FSH levels which however, declined towards the end of the afternoon surge. In conclusion, we suggest that the secretion of LH and FSH is differentially regulated by mu- and kappa-opioid receptors. It is thought that in all groups chloral hydrate interfered with the LH surge secretory systems.     

Organization in photosynthetic membranes of purple bacteria in vivo: The role of carotenoids

Photosynthesis in purple bacteria is performed by pigment–protein complexes that are closely packed within specialized intracytoplasmic membranes. Here we report on the influence of carotenoid composition on the organization of RC–LH1 pigment–protein complexes in intact membranes and cells of Rhodobacter sphaeroides. Mostly dimeric RC–LH1 complexes could be isolated from strains expressing native brown carotenoids when grown under illuminated/anaerobic conditions, or from strains expressing green carotenoids when grown under either illuminated/anaerobic or dark/semiaerobic conditions. However, mostly monomeric RC–LH1 complexes were isolated from strains expressing the native photoprotective red carotenoid spheroidenone, which is synthesized during phototrophic growth in the presence of oxygen. Despite this marked difference, linear dichroism (LD) and light-minus-dark LD spectra of oriented intact intracytoplasmic membranes indicated that RC–LH1 complexes are always assembled in ordered arrays, irrespective of variations in the relative amounts of isolated dimeric and monomeric RC–LH1 complexes. We propose that part of the photoprotective response to the presence of oxygen mediated by synthesis of spheroidenone may be a switch of the structure of the RC–LH1 complex from dimers to monomers, but that these monomers are still organized into the photosynthetic membrane in ordered arrays. When levels of the dimeric RC–LH1 complex were very high, and in the absence of LH2, LD and ?LD spectra from intact cells indicated an ordered arrangement of RC–LH1 complexes. Such a degree of ordering implies the presence of highly elongated, tubular membranes with dimensions requiring orientation along the length of the cell and in a proportion larger than previously observed.     

Characterization of the homologous and heterologous desensitization of rat Leydig-tumour-cell adenylate cyclase.

The homologous and heterologous desensitization of rat Leydig-tumour-cell adenylate cyclase induced by lutropin (LH) was characterized with the aid of forskolin and cholera toxin. Forskolin stimulated cyclic AMP production in a dose-dependent manner, with linear kinetics up to 2h. Forskolin also potentiated the action of LH on cyclic AMP production, but was only additive with cholera toxin. Preincubation of rat Leydig tumour cells with LH (1.0 micrograms/ml) for 1 h produced a desensitization of the subsequent LH (1.0 micrograms/ml)-stimulated cyclic AMP production, whereas the responses to cholera toxin (5.0 micrograms/ml), forskolin (100 microM), LH plus forskolin or cholera toxin plus forskolin were unaltered. In contrast, preincubation with LH for 20h produced a desensitization to all the stimuli tested. When rat Leydig tumour cells were preincubated for 1h with forskolin or dibutyryl cyclic AMP, the only subsequent response that was significantly altered was that to LH plus forskolin after preincubation with forskolin. However, preincubation for 20h with forskolin or dibutyryl cyclic AMP induced a desensitization to all stimuli subsequently tested. LH produced a rapid (0-1h) homologous desensitization, which was followed by a slower (2-8h)-onset heterologous desensitization. Forskolin and dibutyryl cyclic AMP were only able to induce heterologous desensitization. The rate of desensitization induced by either forskolin or dibutyryl cyclic AMP was similar to the rate of heterologous desensitization induced by LH. These results demonstrate that in purified rat Leydig tumour cells LH produces an initial homologous desensitization of adenylate cyclase that involves a cyclic AMP-independent lesion at or proximal to the guanine nucleotide regulatory protein (G-protein). This is followed by heterologous desensitization, which can also be induced by forskolin or dibutyryl cyclic AMP, thus indicating that LH-induced heterologous desensitization of rat Leydig-tumour-cell adenylate cyclase involves a cyclic AMP-dependent lesion that is after the G-protein.     

Effects of weaning and naloxone on luteinizing hormone secretion in postpartum ewes

The effects of weaning and naloxone on concentrations of luteinizing hormone (LH) at 20 days postpartum were examined. March-lambing Finnish Landrace x Southdown ewes (n = 20) were bled via jugular venipuncture at 10-min intervals for 4 h. Naloxone (1 mg/kg bodyweight) was administered i.v. at 60, 120, and 180 min. Treatment groups were suckled (S), weaned on Day 17 (W), suckled plus naloxone (SN), and weaned plus naloxone (WN). Mean concentrations of LH were calculated for 0-60, 70-120, 130-180, and 190-240 min time intervals. Analysis of variance indicated a group effect (p = 0.03) and a group x time interaction (p = 0.02). Concentrations of LH followed a cubic pattern in SN (p = 0.03) and WN (p = 0.08) ewes, whereas LH levels decreased (p less than 0.05) in a pattern consisting of linear and quadratic trends in S and W ewes. Concentrations of LH in S and W ewes were similar at 0-60 and 190-240 min. W ewes had lower (p less than 0.05) concentrations of LH than S ewes at 70-120 and 130-190 min. Further analysis revealed that LH was elevated in SN ewes (p = 0.01) and WN ewes (p = 0.07) at 70-120 min, but was not significantly elevated at 130-180 min. At 190-240 min LH was increased in SN ewes (p = 0.03), but LH levels in WN ewes were similar to those of SN ewes as well as to those of S control ewes.(ABSTRACT TRUNCATED AT 250 WORDS)