Search Results

You are looking at 1 - 7 of 7 items for

  • Author: A J Russell x
  • Refine by Access: All content x
Clear All Modify Search
Free access

Russell A Prough, Barbara J Clark, and Carolyn M Klinge

Dehydroepiandrosterone (3β-hydroxy-5-androsten-17-one, DHEA), secreted by the adrenal cortex, gastrointestinal tract, gonads, and brain, and its sulfated metabolite DHEA-S are the most abundant endogeneous circulating steroid hormones. DHEA actions are classically associated with age-related changes in cardiovascular tissues, female fertility, metabolism, and neuronal/CNS functions. Early work on DHEA action focused on the metabolism to more potent sex hormones, testosterone and estradiol, and the subsequent effect on the activation of the androgen and estrogen steroid receptors. However, it is now clear that DHEA and DHEA-S act directly as ligands for many hepatic nuclear receptors and G-protein-coupled receptors. In addition, it can function to mediate acute cell signaling pathways. This review summarizes the molecular mechanisms by which DHEA acts in cells and animal models with a focus on the ‘novel’ and physiological modes of DHEA action.

Restricted access

R G Sutcliffe, A J Russell, C R W Edwards, and A M Wallace

Understanding of the principal pathways of steroid hormone biosynthesis was established over two decades ago through advances in steroid radioisotopic and chromatographic techniques. When the enzymes of individual pathways could be examined in more detail, the dissection of the complex pattern of enzyme activities began. At many points, separate pathways employ precisely the same enzyme for equivalent catalytic steps, e.g. for 21-hydroxylase, 11 β-hydroxylase, aromatase and several dehydrogenases (Orth et al. 1992). A further economy was found for 17α-hydroxylase and 17,20-lyase activities, which co-purify with the same P450c17 polypeptide. This enzyme was later cloned and expressed in tissue culture cells, revealing that, contrary to the enzyme in rat, human and cattle, 17α-hydroxylase cannot convert 17α-hydroxyprogesterone to androstenedione (Bradshaw et al. 1987, Fevold et al. 1989). Further complexity emerged with the existence of multiple tissue-specific forms of 5α-reductase (Wilson et al. 1993), and 3β-, 11β- and 17β-hydroxysteroid dehydrogenases, most of which

Restricted access

J Tucci, A Russell, P V Senior, R Fernley, T Ferraro, and F Beck


Secretion of parathyroid hormone-related protein (PTHrP) by sheep fetal parathyroid glands is reported to be an important factor in the maintenance of a placental calcium pump. The aim of the present study was to determine whether the developing rat parathyroid glands express PTHrP or parathyroid hormone (PTH), or both. Hybridisation histochemistry was used to detect transcription of PTHrP and PTH in serial paraffin sections through the 12·5- and 13·5-day rat embryo parathyroid anlage, as well as in sections through the 17·5-day embryonic and adult parathyroid glands. Results show strong expression of PTH in the 13·5-day embryonic parathyroid anlage, as well as in the parathyroid gland of the 17·5-day embryo and adult. Transcription of the PTHrP gene was not detected.

The more sensitive technique of reverse transcription PCR was then performed. The pharyngeal region of 11·5-, 12·5- and 13·5-day rat embryos was dissected out and, at each stage, RNA was extracted from these tissues, as well as pooled tissues from the rest of the embryo. RNA that had been extracted from adult thyroid/parathyroid tissue was also tested. After reverse transcription, the resulting cDNAs were amplified by PCR (50 cycles) using specific PTH and PTHrP primers. The results show an abundance of PTH mRNA, specific to the pharyngeal region of the 13·5-day embryo, as well as to adult thyroid/parathyroid tissue. PTHrP expression was detected at very low levels in both parathyroid and extraparathyroid tissues. The presence of immunoreactive PTHrP and immunoreactive PTH in the pharyngeal region and rest of the body of 12·5- and 13·5-day rat embryos was assessed by specific RIAs. Whilst immunoreactive PTHrP was not detected in any of the tissues assayed, immunoreactive PTH was detected only in the pharyngeal region of the 13·5-day embryo. This confirms the results obtained from the gene expression studies.

We conclude then that, in the developing rat embryo, PTH rather than PTHrP is more likely to play a role in calcium regulation. This is in contrast with the reported situation in the sheep, and suggests that fundamental species differences in fetal calcium regulation exist in mammals.

Restricted access

A J Russell, A M Wallace, M G Forest, M D C Donaldson, C R W Edwards, and R G Sutcliffe


A 5-year-old XY pseudohermaphrodite was found to have a defect of steroid biosynthesis consistent with a partial deficiency of the enzyme 3β-hydroxysteroid dehydrogenase (3β-HSD). Circulating concentrations of Δ5 steroids and Δ5 urinary steroid metabolites were elevated and remained elevated after orchidectomy. There was no evidence of salt loss, plasma renin being within normal limits, and no detectable glucocorticoid abnormality. The coding sequences of the genes for 3β-HSD types I and II were amplified by PCR and screened for mutations by denaturing gradient gel electrophoresis (DGGE) and manual and automatic DNA sequencing. A mutation in the gene for 3β-HSD type II was observed at codon 173 (CTA→CGA), leading in the affected patient to a homozygous substitution in which the leucine at residue 173 was altered to an arginine (L173R). The propositus's 2-year-old XX sister was also homozygous for L173R and showed the biochemical characteristics of partial 3β-HSD deficiency without clinical symptoms or signs. The mutation segregated as an autosomal recessive. Three related heterozygous adult females showed evidence of a small over-production of Δ5 steroids and steroid metabolites and a variable reduction in ovarian function. Concentrations of Δ5 steroids and steroid metabolites in the heterozygous father of the propositus were within the normal range.

These data are discussed in relation to the endocrine causes of pseudohermaphroditism and hirsutism. Evidence for tight linkage between the genes for 3β-HSD types I and II was obtained using a microsatellite polymorphism in the third intron of the gene for 3β-HSD type II and synonymous and non-synonymous mutations and polymorphisms in the gene for 3β-HSD type I. The latter polymorphisms were located 88 bp apart at the 3′ end of the type I coding sequence and could be physically resolved as haplotypes using DGGE. The application of DGGE to the analysis of mutations in members of a multigene family is discussed.

Restricted access

M W McBride, A J Russell, K Vass, K Frank-Raue, N J Craig, N Morrison, E Boyd, C Szpirer, and R G Sutcliffe


Four hirsute females from a family exhibiting idiopathic dominant hirsutism were examined. Basal blood levels of Δ5 and Δ4 steroids were within the normal range, but ACTH stimulation led to increases in 17-hydroxypregnenolone and dehydroepiandrosterone that were significantly above control levels. Using polymorphic genetic markers, the genes for cytochrome P450c17 encoded by CYP17, and the type I and II forms of 3β-hydroxysteroid dehydrogenase (3β-HSD) were found not to segregate with hirsutism in this family, though a base substitution was detected in the 3′ end of exon 1 of the gene for 3β-HSD type I in three of the four patients investigated.

Analysis of PCR amplification products by denaturing gradient gel electrophoresis (DGGE) and sequencing revealed a novel homologue of exon 3 of 3β-HSD. DNA of one of the affected patients was used to create a genomic library in λ gem11 and clones containing the novel homologue were obtained and partially sequenced. The equivalent clone was obtained from a genomic library of an unrelated normal individual. The sequences of the clones from patient and control were identical and homologous to exons 2–4 of human 3β-HSD types I and II. No difference was found in the PCR primer sites that flanked the exon 3 homologue which led to its detection on DGGE gels. In both clones, stop codons and deletions were identified in the exon 4 homologue, leading to the deduction that the sequence comes from a pseudogene, which we call 3β-HSD Ψ1. The pseudogene mapped to chromosome 1p13. It was concluded that dominantly inherited idiopathic hirsutism in this rare kindred was not due to deficiencies in 3β-HSD types I, II, or Ψ, or of CYP17.

Open access

Shalinee Dhayal, Kaiyven Afi Leslie, Mohammad Baity, Pouria Akhbari, Sarah J Richardson, Mark A Russell, and Noel G Morgan

During the development of type 1 diabetes, interferons (IFN) are elaborated from islet-infiltrating immune cells and/or from virally infected β-cells. They act via specific receptors to increase, acutely, the phosphorylation of the transcription factors STAT1 and 2. However, the longer-term impacts of chronic IFN stimulation are poorly understood and were investigated in the current study. Human EndoC-βH1 cells were treated with IFNα, IFNγ or IFNλ either acutely (<2 h) or chronically (≥24 h) and STAT phosphorylation, expression and activity were assessed by Western blotting and transcriptional reporter assays. Exposure of β-cells to IFNα or IFNλ induced a swift increase in the phosphorylation of both STAT1 and STAT2, whereas IFNγ increased only pSTAT1. Over more extended periods (≥24 h), STAT phosphorylation declined but STAT1 and STAT2 expression were enhanced in a sustained manner. All IFNs stimulated ISRE transcriptional activity (but with different time courses), whereas GAS activity was responsive only to IFNγ. The re-addition of a second bolus of IFNα, 24 h after an initial dose, failed to cause renewed STAT1/2 phosphorylation. By contrast, when IFNγ was added 24 h after exposure to IFNα, rapid STAT1 phosphorylation was re-initiated. Exposure of β-cells to IFNs leads to rapid, transient, STAT phosphorylation and to slower and more sustained increases in total STAT1/2 levels. The initial phosphorylation response is accompanied by marked desensitisation to the cognate agonist. Together, the results reveal that the response of β-cells to IFNs is regulated both temporally and quantitatively to achieve effective signal integration.

Restricted access

B B Mendonça, A J Russell, M Vasconcelos-Leite, IJ P Arnhold, W Bloise, B L Wajchenberg, W Nicolau, R G Sutcliffe, and A M Wallace


A mutation (A82T) is described in the coding sequence of the gene for 3ß-hydroxysteroid dehydrogenase (3ß-HSD) type II that is associated with variable clinical consequences. Four homozygotes are described, all of which showed elevated levels of Δ5 steroids consistent with 3ß-HSD deficiency. Two males from a consanguineous family were found to be homozygous for A82T and were affected with pseudohermaphroditism. They differed in their degree of mild salt loss. In the same family a female was found to be homozygous for A82T, but was clinically normal and had no history of premature pubarche or of abnormal menstrual cycles. However, in an apparently unrelated family, the A82T mutation was found in a female affected with premature pubarche. This is the first report of a proven mutation in 3ß-HSD type II associated with premature pubarche.