Critical role for glucocorticoid receptors in stress- and ethanol-induced locomotor sensitization

Locomotor sensitization, the augmentation of the locomotor-activating effects of stimuli with repeated exposure, is being evaluated as a partial model for several phenomena including drug addiction. Alteration of dopaminergic systems has been found in sensitized animals and dopamine neurotransmission appears to be crucial for the expression of sensitized behaviors. However, stress hormones, which are released after exposure to many of the stimuli that produce sensitization, may also be involved in the development of this phenomenon. Corticosterone appears to be important in the development of amphetamine sensitization and glucocorticoid receptors (GR) have been hypothesized to mediate this effect. The purpose of these experiments was first, to determine whether repeated restraint stress sensitizes DBA/2J mice to the activating effect of ethanol (EtOH), and second, to explore the role of GR in stress- and EtOH-induced sensitization with the GR antagonist, RU 38486. This antagonist was administered before restraint or i.p. EtOH (1.5 g/kg) on each of 10 consecutive days of pretreatment. In addition, plasma corticosterone levels were determined at various points throughout the pretreatment period and on test days. The results demonstrated that 10 consecutive days of 2-hr restraint sensitized mice to EtOH's locomotor-stimulating effect. Both stress- and EtOH-induced sensitization were attenuated by administration of RU 38486 during the pretreatment phase.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of acute glucose antagonism on hypophyseal hormones and concentrations of insulin-like growth factor (IGF)-I and IGF-binding proteins in serum, anterior pituitary, and hypothalamus of ewes

The objectives of this study were to determine whether 2-deoxy-D-glucose (2DG), a metabolic inhibitor of glucose, 1) differentially affected release of LH, growth hormone (GH) and prolactin (PRL); 2) decreased anterior pituitary response to GnRH; and 3) altered concentrations of insulin-like growth factor I (IGF-I) and intensity of 125I-IGF-I binding to proteins (IGFBPs) in serum, anterior pituitary (AP), and hypothalamus (preoptic are [POA], medial basal hypothalamus [MBH], and stalk median eminence [SME]). In trial 1, mature, ovariectomized, crossbred ewes were treated with a single s.c. injection of either saline (n = 5) or 2DG (n = 5; 0.1 g/kg BW). Administration of 2DG suppressed (p < 0.05) concentrations of LH but did not affect (p > 0.05) serum concentrations of GH or PRL. In trial 2, ovariectomized ewes received injections of saline or 2DG, and each group was subdivided to receive either saline or GnRH analog (5 micrograms; Des-Gly10-[D-Ala6]) 2 h later. Administration of 2DG suppressed (p < 0.05) serum concentrations of LH before administration of GnRH; however, release of LH in response to exogenous GnRH was greater (p < 0.05) in ewes that received 2DG. Treatment with 2DG did not affect (p > 0.05) concentrations of FSH before or after administration of GnRH. In trial 3, 10 ovariectomized ewes were slaughtered 2 h after treatment with saline (n = 5) or 2DG (n = 5). Serum and tissues collected at slaughter (AP, MBH, SME, and POA) were analyzed for concentrations of IGF-I by RIA and intensity of 125I-IGF-I binding to proteins by ligand blotting.(ABSTRACT TRUNCATED AT 250 WORDS)

Neuroactive steroid sensitivity in withdrawal seizure-prone and -resistant mice

Withdrawal Seizure-Prone (WSP) and -Resistant (WSR) mice, which were selectively bred for severe (WSP) or mild (WSR) handling-induced convulsions (HICs) following chronic ethanol inhalation, were found to differ in sensitivity to the anticonvulsant effects of the neuroactive steroid 3 alpha-hydroxy-5 alpha-pregnan-20-one (3 alpha,5 alpha-P. 3 alpha,5 alpha-P (5 or 10 mg/kg, ip) significantly increased seizure thresholds to pentylenetetrazol in ethanol-native males of both the WSP and WSR lines. In general, WSP mice were more sensitive than WSR mice to the anticonvulsant effect of 3 alpha,5 alpha-P. Subsequent studies in male WSP mice exposed to ethanol vapor or air for 24 hr demonstrated enhanced sensitivity to the anticonvulsant effect of 3 alpha,5 alpha-P (0.5-20 mg/kg, ip) during ethanol withdrawal. Only the highest dose affected HICs in air-exposed animals, whereas both the two highest doses significantly reduced HICs in ethanol-exposed mice. These results provide the first demonstration that 3 alpha,5 alpha-P attenuates ethanol withdrawal convulsions and indicate enhanced sensitivity to the anticonvulsant effect of 3 alpha,5 alpha-P in animals withdrawing from ethanol dependence.

Insulin-like growth factor-I (IGF-I) and IGF-binding proteins in bovine sera and pituitaries at different stages of the estrous cycle

The objective of this study was to determine whether concentrations of hypophyseal and serum insulin-like growth factor-I (IGF-I) and binding activities of serum and hypophyseal IGF-binding proteins (IGFBPs) differ with stage of the estrous cycle in mature beef cows. Cows were assigned to the following stages of the estrous cycle based on serum concentrations of progesterone (P4) and ovarian structures at death: days 1-5 (day 0 = estrus; n = 18), days 6-10 (n = 24), days 11-16 (n = 39), and days 17-21 (n = 7). Serum samples collected at death and anterior pituitary homogenates were analyzed for IGF-I, LH, and FSH by RIA. Serum and pituitary IGFBPs were evaluated by ligand and immunoblot analyses. Serum samples contained IGFBP activity at 44 and 40 kilodaltons (kDa; IGFBP-3), 34 kDa (IGFBP-2), 30 kDa (IGFBP-5), 28 kDa, and 24 kDa. The intensity of binding by the different sized proteins in serum remained constant throughout the estrous cycle. IGFBPs detected in anterior pituitaries included a 36-/40-kDa doublet (IGFBP-3), a 32-kDa protein (IGFBP-2), and a 29-kDa IGFBP (IGFBP-5). The intensity of [125I]IGF-I binding to IGFBPs was greater (P < 0.05) during days 11-16 than days 1-5 or days 6-10 of the estrous cycle and was intermediate (P > 0.05) during days 17-21. Serum concentrations of LH were low (< 0.4 ng/ml) during days 1-16 of the estrous cycle, but increased (P < 0.05) approximately 3- to 4-fold during days 17-21. LH concentrations in the anterior pituitary increased (P < 0.05) from the postovulatory period (548 +/- 52 micrograms/g; days 1-5) to the late luteal phase (791 +/- 39 micrograms/g; days 11-16) and were intermediate (P > 0.05) during the preovulatory phase (707 +/- 85 micrograms/g; days 17-21). Concentrations of IGF-I and FSH in the anterior pituitary and serum did not differ (P > 0.05) by stage of the estrous cycle. A positive correlation among the different IGFBPs in the pituitary (P < 0.01) and between each pituitary IGFBP and serum P4 (P < 0.05) existed. The significance (P < 0.0002) of the correlation between pituitary IGFBP-3 and P4 was greater (P < 0.02) than that between the other pituitary IGFBPs and P4. In summary, IGFBP activity in the anterior pituitary, but not that in serum, changed with stage of the estrous cycle in association with serum concentrations of P4. The absence of similar changes in serum or anterior pituitary concentrations of IGF-I supports the hypothesis that IGFBPs may regulate the actions of IGF-I on gonadotropin release from the anterior pituitary gland during the estrous cycle of beef cattle.

Corticosteroids enhance convulsion susceptibility via central mineralocorticoid receptors

Recently, interest in the roles of central nervous system mineralocorticoid receptors (MR) and glucocorticoid receptors (GR) has increased. In vitro results have implicated MR in the enhancing effects of corticosteroids and GR in the suppressing effects of corticosteroids on hippocampal excitability. Although indirect evidence exists suggesting that opposing actions of central MR and GR occur in vivo, direct evidence from studies employing receptor agonists and antagonists is only beginning to emerge. Work in our laboratory suggests that increased corticosterone levels are associated with increased severity of ethanol, pentobarbital, and diazepam withdrawal. Further work with chemical convulsants suggests that MR mediate excitatory effects of corticosteroids on convulsion susceptibility. The circadian rhythm in convulsion susceptibility varies with the circadian rhythm of plasma corticosterone levels and MR binding. The types of convulsions affected by manipulations of MR activity are believed to be of limbic origin, suggesting that limbic convulsions may be alleviated by the use of specific MR antagonists. In addition, because MR are substantially bound at rest and maximally occupied during the circadian peak in corticosteroid levels and during stressor exposure, these receptors are implicated in the maintenance of and in changes in the arousal state of animals.

Relationships among concentrations of steroids, insulin-like growth factor-I, and insulin-like growth factor binding proteins in ovarian follicular fluid of beef cattle

The relationship between ovarian follicular steroidogenesis and insulin-like growth factor binding protein (IGFBP) activity was evaluated during the follicular phase of the bovine estrous cycle. In experiment 1, follicles were collected from cyclic cows (n = 11) slaughtered at 48 h after administration of prostaglandin F2 alpha (PGF; 35 mg i.m.). In experiment 2, cows were injected twice daily with saline (control) or FSH (FSH cows; total dosage = 42 mg) from Day 2 to Day 6 (estrus = Day 0) and with PGF (35 mg i.m.) on Day 7; follicles were collected from control cows (n = 20) slaughtered at 0, 24, 48, or 72 h and from FSH cows (n = 8) at 0 and 48 h after PGF. Follicular fluid was assayed for estradiol (E2), androstenedione (A4), progesterone (P4), and insulin-like growth factor-I (IGF-I) by RIA and for IGFBP activity by ligand blotting and densitometry. Intensities of the 34-kDa (IGFBP-2), 29-27-kDa, and 22-kDa IGFBP bands in follicular fluid were nondetectable or were lower (p < 0.01) in the fluid of large (> or = 8 mm) E-active (E-A; E2 > 50 ng/ml and > P4) follicles than in large E-inactive (E-I), medium (5-7 mm), or small (< 5 mm) follicles. IGFBP-3 (44-40-kDa doublet) was unaffected by follicle stage in experiment 1, but IGFBP-3 was lower (p < 0.01) in follicular fluid of E-A vs. E-I large follicles in experiment 2. Profiles of IGFBP activity were similar in follicular fluid of small, medium, and E-I large follicles. In experiment 2, E2 concentrations in large E-A follicles increased (p < 0.01) from 0 to 48 h after the PGF injection for control cows but decreased (p < 0.01) for FSH cows, whereas follicular fluid IGFBP-2 binding activity decreased from 0 to 48 h after PGF in controls and increased in FSH cows (treatment x time, p < 0.05). IGFBP-3 binding was unaffected by FSH treatment or time after administration of PGF. Profiles of IGFBP activity in homogenates of granulosa or theca cells were similar to follicular fluid profiles except for the absence of IGFBP-3 binding activity. The disappearance of binding activities for IGFBP-2 and smaller-molecular-mass IGFBPs in E-A follicles suggests a possible regulatory role for IGFBPs in follicular maturation and on aromatase activity.(ABSTRACT TRUNCATED AT 400 WORDS)

Follicular development and superovulation response in cows administered multiple FSH injections early in the estrous cycle

To determine whether follicular development, superovulation and embryo production were affected by the absence or presence of a dominant follicle, cows were administered injections of FSH twice daily in the early (Days 2 to 6, estrus=Day 0) or middle stage (beginning on Day 10 or 11) of the estrous cycle. Treatment with FSH early in the cycle stimulated follicular development in 83 to 100% of all cows from 4 groups evaluated at different times after PGF2alpha treatment on Days 6 and 7. However, the proportion of cows with >2 ovulations varied from 31 to 62.5%, indicating that induction of follicular development may occur in the absence of superovulation. When compared with cows treated in the middle of the cycle, no differences were observed in the proportion of cows with >2 ovulations (31 vs 20%), ovulation rate. (26.0+/-6.3 vs 49.6+/-25.8), production of ova/embryos (13.3+/-3.2 vs 14.4+/-3.4), or the number of transferable embryos (8.0+/-3.6 vs 5.4+/-1.5; early vs middle, respectively). The proportion of the total number of embryos collected that were suitable for transfer was greater (P<0.01) in cows treated early in the cycle (60%) than at midcycle (37.5%). The diameter of the largest follicle observed by ultra-sound prior to initiation of FSH treatment in the early stage of the cycle (10.0+/-2.0 mm) was smaller (P<0.05) than at midcycle (16.8+/-1.3 mm). These results demonstrate that superinduction of follicular development is highly consistent after FSH treatment at Days 2 to 6 of the cycle and that superovulation and embryo production are not less variable than when FSH is administered during the middle of the cycle. However, superovulation in the early stage of the cycle may increase the proportion of embryos suitable for transfer.

Sensitivity of the circadian rhythm of kainic acid-induced convulsion susceptibility to manipulations of corticosterone levels and mineralocorticoid receptor binding

Increases in corticosterone levels have been associated with enhanced susceptibility and decreases in corticosterone levels have been associated with decreased susceptibility to convulsions in mice. The proconvulsant effects of corticosterone are believed to be mediated by central mineralocorticoid receptors (MR). Both convulsion susceptibility and plasma corticosteroid levels display circadian rhythmicity. When corticosterone levels are at their lowest, hippocampal MR binding is submaximal, whereas when corticosterone levels are at their circadian peak, hippocampal MR binding is maximal. In the present experiments the relationship between circadian rhythms of susceptibility to kainic acid-induced convulsions and plasma corticosterone levels was investigated. In addition, the effects of exogenously administered corticosterone and the MR antagonist spironolactone were examined at times of different convulsion susceptibility. In general, lower plasma corticosterone levels were associated with decreased convulsion susceptibility and higher plasma corticosterone levels were associated with greater convulsion susceptibility. Corticosterone, administered when endogenous levels were low, had a proconvulsant effect. Spironolactone, administered when corticosterone levels were higher and hippocampal MR were presumably maximally occupied, had an anticonvulsant effect. These results indicate that the circadian rhythm in susceptibility to kainic acid-induced convulsions is sensitive to manipulations of corticosterone levels and MR binding. Degree of central MR occupancy may, in part, mediate convulsion susceptibility in humans as well as laboratory animals.

Mineralocorticoid receptors mediate the enhancing effects of corticosterone on convulsion susceptibility in mice

With hippocampal slice electrophysiology, direct evidence that mineralocorticoid receptors (MR) mediate excitatory effects of corticosteroids on neuronal activity was found. The present experiments extended this hypothesis to a whole animal model. The effects of manipulations of MR binding on convulsions produced by pentylenetetrazol (PTZ), strychnine and kainic acid were examined. Moderate increases in plasma corticosterone levels resulted in enhanced susceptibility to several convulsion types; decreased levels attenuated the susceptibility. The proconvulsant effects of corticosterone were inhibited by the MR antagonist, spironolactone. Convulsions typically affected by these manipulations were PTZ-induced myoclonic jerk and face and forelimb clonus and kainic acid-induced convulsions. Other convulsion types, e.g., PTZ-induced running bouncing clonus and tonic hindlimb extension and strychnine-induced convulsions, were generally unaffected by these manipulations, which suggests that central MR effects are not global. The convulsions that were sensitive to MR manipulations are believed to originate in limbic structures. These results provide the first direct evidence for a role of central MRs in the modulation of central nervous system excitability in a whole animal. Furthermore, they suggest that central MR action may be important in disruptions of excitability, such as epilepsy, drug withdrawal syndromes and arousal states in healthy animals.

In vitro production of estradiol by bovine granulosa cells: evaluation of culture condition, stage of follicular development, and location of cells within follicles

In vitro estradiol (E2) production by bovine granulosa cells was evaluated under several culture conditions, which included the presence or absence of fetal bovine serum (FBS; 2.5 and 10%), serum substitutes (1% Nutridoma [Boehringer-Mannheim, Indianapolis, IN], 2% UltroSer G [IBF Biotechnics, Villenue-la Garenne, France]), selenium (Se; 10 ng/ml), lipoprotein (0.25% Excyte/ml), O2 concentration (5 and 20%), and two attachment factors (Pronectin F and PepTite-2000). Dulbecco's Modified Eagle's medium:Ham's F-12 medium (1:1 mixture) containing 1 microM androstenedione, 1 microgram/ml insulin, and 0.1% BSA was the basal medium evaluated. The optimum conditions determined were the basal medium in 5% O2. These conditions were then used to ascertain whether or not E2 production by granulosa cells varied with respect to location of cells within a follicle. Follicular fluid was aspirated and centrifuged to obtain granulosa cells expected to be primarily luminal and cumulus cells. Follicles were then bisected, and remaining mural granulosa cells were removed by scraping the follicle wall with a fine plastic loop. Aspirated granulosa cells secreted more (p < 0.01) E2 than scraped cells. Production of E2 during Days 0 to 2 of culture by aspirated (0.15 +/- 0.05 ng/microgram DNA) and scraped (0.02 +/- 0.01 ng/microgram DNA) granulosa cells from small follicles (< 8 mm) was less than that by aspirated (6.30 +/- 2.20 ng/micrograms DNA) and scraped cells (1.90 +/- 1.00 ng/microgram DNA) from large follicles (> or = 8 mm). During Days 2 to 4 of culture when compared to Days 0 to 2, E2 production increased for aspirated (but not scraped) granulosa cells from small follicles (0.66 +/- 0.23 ng/microgram DNA)). In contrast, E2 production decreased (p < 0.05) over time in culture for aspirated (2.10 +/- 0.50 ng/microgram DNA) and scraped (0.16 +/- 0.07 ng/microgram DNA) granulosa cells from large follicles. Thus, granulosa cells proximal to the basement membrane may be less differentiated with regard to E2 production than cells distal to the basement membrane. In addition, aspirated granulosa cells from small follicles appear to continue to differentiate toward E2-producing cells during culture, a characteristic difficult to obtain with bovine granulosa cells.

Corticosterone increases severity of acute withdrawal from ethanol, pentobarbital, and diazepam in mice

It has been suggested that withdrawal from several subclasses of central nervous system (CNS) depressants involves common underlying mechanisms. For example, mice genetically selected for severe ethanol withdrawal convulsions (Withdrawal Seizure Prone or WSP) have also been found to express severe withdrawal following treatment with barbiturates and benzodiazepines. Corticosteroids appear to modulate severity of withdrawal from CNS depressants. Therefore, it was hypothesized that corticosterone would enhance withdrawal convulsions following acute ethanol, pentobarbital, and diazepam in WSP mice. Corticosterone (20 mg/kg) administered following each of these drugs significantly increased severity of handling-induced convulsions during withdrawal. Corticosterone did not affect pre-withdrawal convulsion scores or handling-induced convulsions of drug-naive mice. These results suggest that withdrawal convulsions following acute ethanol, pentobarbital, and diazepam are sensitive to modulation by corticosterone and they support the hypothesis that stress may increase drug withdrawal severity.

Type I corticosteroid receptors modulate PTZ-induced convulsions of withdrawal seizure prone mice

Corticosteroids have been shown to modulate convulsion expression in humans and animals. It is hypothesized that type I corticosteroid receptors mediate the excitatory effects of corticosteroids in vivo based on low-dose efficacy of corticosterone, and differential effects of mineralocorticoids vs. glucocorticoids on convulsions. In the present experiments, the effects of altering corticosterone levels, and the role of the type I receptor in mediating these effects, were examined using pentylenetetrazol (PTZ)-induced convulsions in ethanol withdrawal seizure prone (WSP) mice. It was hypothesized that stimulation of type I receptors partially mediates the expression of tonic hindlimb extensor (THE) convulsions produced by PTZ. Aminoglutethimide, a steroid synthesis inhibitor, increased latencies to PTZ-induced THE. This anticonvulsant effect was reversed by corticosterone and the type I agonist, deoxycorticosterone (DOC), but not by the type II agonist, dexamethasone. Furthermore, two type I receptor antagonists, spironolactone and RU26752, increased latencies to PTZ-induced THE, suggesting that they have anticonvulsant action. In summary, the results of these experiments suggest that type I corticosteroid receptors are important for expression of PTZ-induced convulsions.

Dissociation of the effect of aminoglutethimide on corticosterone biosynthesis from ataxic and hypothermic effects in DBA and C57 mice

Adrenalectomy is frequently used to deplete adrenocortical hormones in physiological and receptor-binding studies in animals. However, this procedure is irreversible, removes both the cortex and medulla, and produces many negative side effects such as hypotension and hypoglycemia. Aminoglutethimide is a steroid synthesis inhibitor which depletes adrenocortical hormones without these negative effects. However, aminoglutethimide itself has been shown to produce behavioral and physiological deficits. In the present experiments, dose-response relationships were determined for the effects of aminoglutethimide on corticosterone levels, motor coordination, and body temperature in C57 and DBA mice. Aminoglutethimide (5.4-54 mg/kg) inhibited the increase in plasma corticosterone concentrations normally observed in response to restraint stress. Only at higher doses (170-1,000 mg/kg) were rotarod performance and body temperature affected. The corticosterone response to restraint stress recovered fully between 12 and 24 h after aminoglutethimide. In the present study, doses of aminoglutethimide were found that temporarily inhibit stressed corticosterone release without producing motor deficits and temperature decreases. These results indicate that aminoglutethimide is a potential substitute for adrenalectomy in studies on the effects of removal of adrenocortical hormones.

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Genetic differences in hypothalamic-pituitary-adrenal axis responsiveness to acute ethanol and acute ethanol withdrawal

There is a growing body of evidence suggesting that corticosteroids contribute to the increased neural excitability observed during ethanol withdrawal. In the present study, this was further investigated using mouse strains which differ in ethanol withdrawal severity. DBA/2 (DBA) mice were found to display more severe acute ethanol withdrawal seizures than C57BL/6 (C57) mice. Additionally, DBA mice showed a greater stress response than C57 mice, as measured by higher plasma concentrations of adrenocorticotropic hormone (ACTH) and corticosterone, to an acute dose of ethanol. Mimicking withdrawal plasma corticosterone levels by administering corticosterone to ethanol-naive mice resulted in increases in handling-induced convulsions in the range observed during withdrawal. There did not appear to be a strain difference in sensitivity to the excitatory effects of corticosterone. In summary, the greater stress response to ethanol by DBA mice may account, in part, for the more severe ethanol withdrawal syndrome of this strain.

Induction of experimental autoimmune uveoretinitis in Lewis rats with purified recombinant human retinal S-antigen fusion protein

Full-length human retinal cDNA for S antigen (S-ag) and for the alpha subunit of transducin (alpha-Td) were subcloned into a bacterial expression plasmid vector to generate recombinant fusion proteins with glutathione-S-transferase (GST). The recombinant GST-S-ag and rGST-alpha-Td fusion proteins were purified from bacterial extracts by continuous flow preparative gel electrophoresis under denaturing conditions, and were assessed for their ability to induce experimental autoimmune uveoretinitis (EAU). Immunization of Lewis rats with single doses of 10 micrograms-100 micrograms rGST-S-ag in Freund's complete adjuvant supplemented with Bordetella pertussis readily induced clinical signs of EAU. Immunization with GST alone did not induce EAU indicating that disease activity was ascribable to the S-ag residues in the fusion protein. Although the alpha-Td shares limited sequence homology with S-ag, the rGST-alpha-Td fusion protein was also not uveitogenic in Lewis rats. The clinical severity of EAU in Lewis rats sensitized with rGST-S-ag was found to be milder than that induced with native S-ag preparations purified from human retina. However, humoral antibody responses to sensitization with the recombinant S-ag fusion protein were of a higher magnitude than with native S-ag. The availability of recombinant preparations of human S-ag protein will be of value in studying its processing and presentation to T cells derived from patients with autoimmune retinal vasculitis.

Pathogenicity and immunogenicity of recombinant human retinal S-antigen fusion protein

A full-length cDNA clone to human S-antigen (HS-ag) was isolated from lambda gt 10 human retinal library and expressed as a fusion protein with glutathione S-transferase (GST) in E. Coli. Uveitogenicity and immunogenicity of recombinant GST-HS-ag fusion protein and native HS-ag were compared in EAU-susceptible Lewis rats. Recombinant HS-ag was found less uveitogenic than native HS-ag. Animals inoculated with recombinant HS-ag developed EAU on day 17, three days later than those inoculated with native HS-ag, the incidence of the disease was reduced from 80% to 58% and the score of clinical severity reduced from 2.2 to 1.3 points respectively. In contrast, rGST-HS-ag was more immunogenic than native HS-ag as it elicited four times higher levels of antibodies which reacted specifically with both antigens.

Transforming growth factor-alpha and -beta differentially regulate growth and steroidogenesis of bovine thecal cells during antral follicle development

The actions and interactions of transforming growth factor-alpha (TGF alpha) and TGF beta on growth and differentiation of bovine thecal cells were investigated. Bovine thecal interna cells were isolated from small (less than 5 mm), medium (5-10 mm), and large (greater than 10 mm) antral follicles and cultured in the presence or absence of TGF alpha and/or TGF beta. Both [3H]thymidine incorporation and changes in cell number (i.e. DNA levels) were evaluated to determine effects on thecal cell growth. Short term treatment of cells with TGF alpha (18-24 h) stimulated thymidine incorporation, and longer term treatments (4 days) increased cell number. TGF beta suppressed thymidine incorporation below that observed in untreated cultures, but had no effect on cell number. When combined with TGF alpha, TGF beta suppressed the ability of TGF alpha to stimulate thymidine incorporation and increase cell number. The response to these growth factors was similar for cells isolated from the different stages of antral follicle development. The effects of TGF alpha and TGF beta on thecal cell differentiation were evaluated by quantitating changes in androstenedione and progesterone accumulation in cultures treated with TGFs in the absence (basal) or presence of hCG, estradiol (E2), or a combination of hCG and E2. E2 and hCG were included in this study because previous research has demonstrated that these hormones alter thecal cell steroidogenesis. Treatment with TGF alpha resulted in a suppression of basal and hormonally stimulated accumulation of androstenedione during days 0-3 of culture, whereas TGF beta did not significantly alter androstenedione accumulation. TGF alpha also suppressed progesterone accumulation during days 0-3 of culture in the absence or presence of hormones. In contrast, TGF beta stimulated accumulation of progesterone in cultures that did not contain E2, which suppressed progesterone during this period. Therefore, during days 0-3 of culture, TGF alpha appears to have suppressive effects on androstenedione and progesterone production, whereas TGF beta can stimulate progesterone production in the absence of E2. During days 3-6 of culture, thecal cell differentiation changes, and the capacity to produce androstenedione dramatically declines, while the capacity to produce progesterone increases. During this period, either TGF alpha or TGF beta slightly increased basal progesterone accumulation and partially suppressed the ability of hCG to stimulate progesterone. The effects of TGFs on thecal cell steroidogenesis were similar with cells isolated from the different stages of antral follicle development. Results from these studies provide evidence that THF alpha and TGF beta can modulate thecal cell growth and differentiation (i.e. steroidogenesis).(ABSTRACT TRUNCATED AT 400 WORDS)

Differential modulation by the stress axis of ethanol withdrawal seizure expression in WSP and WSR mice

Withdrawal from both acute and chronic ethanol (EtOH) exposure is associated with increased neural excitability and increased activity of the hypothalamic-pituitary-adrenal axis. There is some evidence that glucocorticoids are necessary for EtOH withdrawal seizure expression. Lines of mice that were selected for severe (WSP) and minimal (WSR) EtOH withdrawal (as estimated from handling-induced convulsion scores) have been shown to differ in their stress response following an acute dose of EtOH. In this study we provide evidence that these lines of mice also differ in their sensitivity to the excitatory effects of glucocorticoids. EtOH withdrawal seizures of WSP mice were significantly increased by chronic and acute corticosterone treatment, whereas those of the WSR mice were unaffected. Neural excitability was decreased in the WSP mice when aminoglutethimide, a glucocorticoid synthesis blocker, was administered. Thus, it appears that genetic differences in EtOH withdrawal seizure severity may be due, in part, to differences in sensitivity to the excitatory effects of glucocorticoids.

Quantity and quality of embryos collected from mice passively immunized against estradiol

The objective of this study was to determine the effects of passive immunization against estradiol on the occurrence and timing of estrus, ovulation and fertilization rates and on early embryonic development in mice. Swiss Webster female mice were randomly assigned to one of the three treatment groups to be injected with 0.1 ml saline (control; n=15), 0.1 ml anti-estradiol antisera (high dose: n=17) or 0.1 ml antiestradiol antisera diluted 1:10 with saline (low dose; n=17) at seven weeks of age. Immediately after injection mice were placed with males and observed daily for the presence of vaginal plugs for 10 d. Three days after vaginal plugs were observed, mice were terminated and the uteri were removed and flushed to determine the number and quality of unfertilized ova and embryos. No differences were observed in the timing of vaginal plug formation, the proportion of mice with vaginal plugs, or the mean number of unfertilized ova or embryos collected from each treatment group. However, the proportion of excellent or good quality embryos was reduced in the high dosage treatment. It was concluded from this study that passive immunization of mice against estradiol did not increase the number of embryos obtained from mice and that a high dosage of antisera against estradiol reduced embryo quality. These results provide evidence that alterations in levels of estradiol may adversely affect embryonic development.

Reproductive and endocrine changes in ewes actively immunized against estrogens and androgens

Twenty ewes were divided equally into two treatments to be actively immunized simultaneously against estrogen and androgen conjugated to ovalbumin (steroid immunized) or immunized against ovalbumin alone (control) to determine the effects of steroid immunization on reproduction and pituitary function. Ewes were immunized at week 0, 3 and 5 of the 93-week study and exposed to a fertile ram for two breeding seasons (weeks 7-25 and weeks 60-67). Steroid immunization reduced the proportion of ewes which exhibited estrus during the first breeding season when antibody activity against steroids was highest and reduced the proportion of ewes lambing after both breeding seasons. Ovulation rate, observed only during the second breeding season, was two times higher in steroid immunized ewes, but no increase in percent lamb crop per ewe lambing was observed. Pituitary concentrations of immunoactive LH (determined by radioimmunoassay), bioactive LH (determined by stimulation of mouse Leydig cell production of testosterone) and receptors for LHRH were increased by steroid immunization. These changes in pituitary LH resulted in a decreased ratio of bioactive to immunoactive LH observed in the pituitary and a decrease in circulating concentrations of bioactive LH. It was concluded from this study that simultaneous active immunization against estrogens and androgens increases ovulation; however, estrus and lambing rates may be reduced when antibody activity is high. Ovulation rates were increased despite the fact that no change in FSH was observed and the biopotency of LH was decreased in steroid immunized ewes.

Hormonal regulation of thecal cell function during antral follicle development in bovine ovaries

The hormonal regulation of thecal cell function was investigated with cells isolated at various stages of antral follicle development. Bovine thecal cells were isolated from small antral, medium antral, and large Graffian follicles (small, medium, and large ovarian follicles). Serum-free cultures of thecal cells were established and viable for a minimum of 6-8 days of culture. The purity of the thecal cell population was characterized cytochemically and was found to contain less than 5% endothelial cell and/or granulosa cell contamination. The steroidogenic capacity of this purified population of thecal cells in serum-free culture was examined through an analysis of androgen and progesterone production. Androgen production was high during the first 3 days of culture, then declined to undetectable levels. Production of androstenedione was approximately 10-fold higher than production of testosterone. Progesterone production remained relatively constant throughout the 8-day culture period. hCG was found to stimulate androgen production during days 1-3 of culture, but had a negligible effect on progesterone production. In contrast, hCG stimulated progesterone production during days 3-6 of culture, but had a negligible effect on androgen production. Insulin stimulated progesterone production during days 3-6 of culture, but had no effect on androgen or progesterone production during days 1-3 of culture. The minimum effective concentrations of hCG and insulin required to stimulate steroidogenesis of the thecal cells ranged from approximately 1-10 ng/ml. Addition of serum to the cultures decreased androgen production and suppressed the hormone responsiveness of the cells. Thecal cells in culture appear to alter their steroidogenic capacity from an androgen-producing cell to a progesterone-producing cell. Analysis of the developmental regulation of thecal cell function revealed that androgen production and hormone responsiveness were relatively constant in small, medium, and large follicles. In contrast, progesterone production and hormone responsiveness were highest in small follicles, intermediate in medium follicles, and lowest in large follicles. A more general analysis of the developmental regulation of thecal cell function examined the secretion of radiolabeled proteins. A large number of radiolabeled proteins were secreted by thecal cells, ranging in molecular mass from 5-500 kDa. Interestingly, insulin and hCG had no major effect on secretion of proteins by cells isolated from any of the stages of development examined.(ABSTRACT TRUNCATED AT 400 WORDS)

Estrogen regulation of thecal cell steroidogenesis and differentiation: thecal cell-granulosa cell interactions

Estrogen regulation of thecal cell steroidogenesis and differentiation was investigated with cells from ovarian antral follicles. Bovine theca interna cells were isolated and cultured in serum-free conditions to evaluate the effects of estradiol on thecal cell production of androstenedione, testosterone, and progesterone. Estradiol increased thecal cell androgen production throughout a 6-day culture period; however, the basal and stimulated levels of androgen production diminished after day 3 of culture. Androstenedione accumulation was approximately 10-fold greater than that of testosterone. In contrast to the stimulatory effects that estradiol had on androgen production, estradiol suppressed progesterone production throughout the 6-day culture period. Comparison of the effects of estradiol and hCG on thecal cells from small (less than 5 mm), medium (5-10 mm), and large (greater than 10 mm) antral follicles demonstrated that estradiol stimulated androgen production to a greater extent than hCG with cells from all of these stages of follicle development. Estradiol stimulation of androstenedione was greater in theca from small follicles than in theca from medium or large follicles. In contrast, suppressive effects of estradiol on progesterone were most apparent on thecal cells from medium and large follicles and less apparent on theca from small follicles. Estradiol stimulated androstenedione production in a dose-dependent fashion, with a minimum effective concentration of 10(-9) M and a maximum effective concentration of 10(-7)-10(-6) M. Concentrations greater than 10(-6) M estradiol resulted in a decline in the stimulatory response and may be important in the preovulatory follicle to suppress thecal cell androgen production and initiate the process of luteinization. Progesterone production was slightly stimulated by 10(-9) M estradiol, whereas higher concentrations (10(-7)-5 x 10(-6) M) resulted in a dose-dependent suppression of progesterone production. Interestingly, combined treatment of thecal cells with estradiol and hCG resulted in a greater than additive stimulation of androstenedione production, and estradiol decreased the ability of hCG to stimulate progesterone production. Observations demonstrate that estradiol can dramatically alter thecal cell production of steroids and support a hypothesis that steroid-mediated interactions between granulosa and thecal cells play an important role in regulating cellular function within follicles. The data provide evidence that a local feedback loop may exist in ovarian follicles, where androgens produced by thecal cells are used as a substrate for granulosa cell aromatization into estrogens, which, in turn, may feed back to stimulate thecal cell production of androgens.(ABSTRACT TRUNCATED AT 400 WORDS)