Steroid 21-hydroxylase expression in cultured rat astrocytes

Over the past decade or so it has become widely recognised that the brain is a significant steroidogenic organ. Many publications have highlighted the ability of the brain to synthesise and interconvert a large number of steroid products including cholesterol, progesterone and testosterone. In this study, in vitro experiments were performed to determine if 21-hydroxylation of steroids is undertaken by rat brain astrocytes in culture. This is a common reaction that occurs in the adrenal gland and other organs in mammals, catalysing the conversion of pregn-4-ene-3,20-dione (progesterone) to 21-hydroxypregn-4-ene-3,20-dione (deoxycorticosterone).

Previous reports have indicated that 21-hydroxylation occurs within the rat brain, however, the precise identity of the cells expressing 21-hydroxylase has not yet been determined. Several metabolites, such as 5α-pregnan-3α-ol-20-one (tetrahydroprogesterone) and 3α,21-dihydroxy-5-pregnan-20-one (tetrahydrodeoxycorticosterone) were of particular interest because of their modulatory role in neuronal function, such as their agonist activity at γ-aminobutyric acid (GABA_A) receptors.

Evidence was obtained for the expression of peripheral 21-hydroxylase enzyme (P450c21) in cultured rat brain astrocytes by a combination of mass spectroscopy and molecular biology techniques. This is a significant finding as expression of 21-hydroxylase within astrocytes may be indicative of a wider role for these cells in modulating neuronal behaviour.

Environmental factors affecting transcription of the human L1 retrotransposon. I. Steroid hormone-like agents

The L1 retrotransposon has significantly shaped the structure of the human genome. At least 30% of human genome sequence can be attributed to L1 reverse transcriptase activity. There are 105 copies of the human L1 retrotransposon, L1Hs, most of which are defective, although ~8–9x103 are full length. L1Hs elements transpose through an RNA intermediate and transcription is thought to be the rate limiting step in retrotransposition. Because transcription of retrotransposons in a variety of organisms has been shown to respond to environmental stimuli, we investigated the influence of various agents on transcription from two different L1Hs promoters. The activity of the L1Hs promoters was analyzed by transfecting L1Hs-expressing cell lines with plasmids containing the L1Hs promoters fused to the LacZ reporter gene and monitoring expression with a ß-galactosidase assay. Small increases in ß-galactosidase activity were observed with both L1Hs promoters after treatment with serum, testosterone, dihydrotestosterone and organochloride pesticides, indicating that these agents can influence L1Hs transcription.

Single vs. two steroid injections for carpal tunnel syndrome: a randomised clinical trial

We investigated the efficacy of a single vs. double steroid injections in the treatment of carpal tunnel syndrome (CTS) in a randomised double-blind controlled trial. Patients with idiopathic CTS were randomised into (i) one group receiving a baseline methylprednisolone acetate injection plus a saline injection 8 weeks later and (ii) a second group receiving methylprednisolone acetate injection at baseline and at 8 weeks. The primary outcome was the Global Symptom Score (GSS). Forty patients were recruited. By 40 weeks, the mean GSS improved from 25.6 to 14.1 in the single-injection group whereas from 26.7 to 12.6 in the reinjection group, but there was no significant difference in GSS between the two groups (p = 0.26). There were also no significant differences in terms of electrophysiological and functional outcomes. The results suggest that an additional steroid injection confers no added benefit to a single injection in terms of symptom relief.

Is sex-specific mass gain in Cory's shearwaters Calonectris diomedea related to begging and steroid hormone expression?

Mass differences between the sexes of dimorphic bird species often appear early in the nestling development. But how do adults know how much to feed a chick in a sexually dimorphic species? Do chicks of the heavier sex beg more? We studied begging in Cory’s shearwaters Calonectris diomedea, a species with heavier adult and juvenile males than females. We found that begging rates and call numbers were not different between male and female chicks, but parameters of begging intensity differed between the sexes in their relationship to chick body condition. For the same body condition, males had significantly higher begging call numbers and rates. Acoustical parameters, which were analysed semi-automatically, included the lengths of call and silence intervals, the minimum, mean and maximum frequency in a call and the number of frequency peaks within a call. We found no consistent differences of acoustic begging call elements between the sexes. Male and female chicks did not differ in the levels of the steroid hormones testosterone or corticosterone in the second quarter of the nestling period, and the mechanism leading to sex-related differences in begging rates for a given body condition remains unknown.

Cortisol delays the estradiol-induced LH surge : is this dependent on prior ovarian steroid exposure?

Glucocorticoids can inhibit pulsatile LH secretion and can delay or even block the preovulatory LH surge. Previous work in ovariectomized ewes has indicated that cortisol can delay the estradiol-induced LH surge in an artificial follicular phase model but the results suggest this effect may be influenced by prior exposure to ovarian steroids. Here we tested the hypothesis that this disruptive effect of cortisol on the positive feedback action of estradiol is dependent on prior exposure to the ovarian steroidal milieu of the estrous cycle. Using long-term ovariectomized ewes, sequential artificial estrous cycles were created in the anestrous season by treatment and subsequent withdrawal of progesterone (CIDRs inserted for 9 d) followed by estradiol implants simulating the pre-ovulatory estradiol rise that induces the LH surge. Following the first artificial estrous cycle, a second cycle was initiated. Progesterone was again administered for 9 d followed by a second artificial follicular phase two weeks later. Beginning 2 hr prior to estradiol administration and ending at 40 hr, animals received either a cortisol infusion (elevate plasma levels to ∼170 ng/ml) or vehicle. Jugular blood was sampled hourly to assess occurrence and timing of the LH surge. Four different treatment sequences were tested (Cycle 1-Cycle 2): cortisol-cortisol; vehicle-cortisol; cortisol-vehicle; and vehicle-vehicle (n=5-6/sequence). If prior exposure to the ovarian steroidal milieu of the estrous cycle was necessary for cortisol to interfere with the positive feedback action of estradiol, then we would predict that cortisol would only delay the LH surge when it was delivered in Cycle 2 but not Cycle 1. Our results failed to support this prediction. Cortisol delayed the surge in both cycles (p<0.01), and the extent of the delay was the same in both Cycles 1 and 2 (4 hrs). Cortisol did not significantly affect surge amplitude in either cycle. These findings reinforce our previous conclusion that cortisol can delay the estradiol-induced LH surge but they do not support the hypothesis that this action of cortisol is dependent upon exposure to the ovarian steroidal milieu of the previous estrous cycle. (NIH-HD-30773)

Steroid metabolism in cultured mammalian astrocytes

This thesis explores the metabolism of the steroid progesterone within both rat and mouse brain cells in culture. The research identified a steroid 21-hydroxylase within the rat culture system, that has downstream implications on stress and behaviour. Novel uses for a stain to accurately discriminate two brain celltypes were discovered.

Steroid acyl transferase activity in the mammalian brain

This thesis investigates steroid fatty acid esters (which may have a possible role in myelination of the central nervous system) in mammalian brain. While these conjugates are abundant in brain tissue, little is known about their biological role. When measuring steroid acyl transferase activity, the optimum substrate concentration was found to vary significantly between the sheep and rat brain. Results also indicated that different enzymes may act to esterify different steroid substrates.

Predicting future anabolic-androgenic steroid use intentions with current substance use : findings from an internet-based survey.

OBJECTIVE: To explore how current substance use, including the use of sports supplements and illicit drugs, may impact upon a person's future intentions to use anabolic-androgenic steroids (AAS).

DESIGN: Web-based survey.

PARTICIPANTS: Two hundred fourteen exercising males (mean age, 30 years; range, 17-61 years) recruited from 5 gymnasia in Sydney, Australia, completed a web-based survey. The survey contained questions relating to sport supplement use, illicit substance use, reasons for currently not using AAS, and reasons for intending to use AAS in the future.

INTERVENTIONS: Participants completed a structured interview schedule that included questions regarding licit and illicit substance use, reasons for non-AAS use, and, where appropriate, reasons for intended future AAS use.

MAIN OUTCOME MEASURES: The planned main outcome measure was positive intention to use AAS.

RESULTS: Sixteen percent of the sample indicated that they would use AAS in the future. Reasons for future AAS use included increasing muscle size (80%), improving appearance (74%), and increasing strength (57%). Four-fifths (80%) of the sample reported use of sports supplements, with vitamins and protein supplements commonly reported (83% and 67%, respectively); more than one-third (36%) reported use of creatine in the past 6 months. Half (52%) of the sample reported use of illicit substances in the preceding 6 months, with amphetamines and cannabis commonly reported (66% and 62%, respectively). Significant predictors of intending to use AAS included past 6-month use of creatine and knowing AAS users.

CONCLUSIONS: The use of sport supplements and/or illicit substances may remove barriers for the future use of such drugs as AAS. Future research is necessary to explore in depth whether such substances may act as a "gateway" to future AAS use.

Effects of the aromatase inhibitor Fadrozole on plasma sex steroid secretion and oocyte maturation in female coho salmon (Oncorhynchus kisutch) during vitellogenesis

17β-estradiol, 17α-20β-dihydroxy-4-pregnen-3-one (17α-20β-P), and testosterone levels were measured in plasma samples obtained from vitellogenic coho salmon (Oncorhynchus kisutch) before and 32 days after injection of the aromatase inhibitor Fadrozole (AI). Plasma 17β-estradiol levels decreased significantly 6 h after injection in all AI treated fish. The higher the dose the longer the maintenance of low plasma 17β-estradiol levels. Inversely, plasma 17α-20β-P increased significantly 6 h after injection in all AI treated fish, and the higher the dose the longer the maintenance of high plasma 17α-20β-P levels. At 48 h after injection plasma testosterone levels were significantly higher in the AI treated groups. The oocyte maturation index showed that multiple injections with AI retarded oocyte development. Besides, oocyte diameter and GSI were lower in the same group, which presented high incidence of atresia of vitellogenic oocytes. The ovarian follicles and brain of the fish which received multiple injections secreted less 17β-estradiol, in vitro. These findings suggest that aromatase inhibitors such as Fadrozole may have a potential as a tool to regulate sexual development in salmon.