Glucocorticoid metabolism by 11-beta hydroxysteroid dehydrogenase type 2 modulates human mineralocorticoid receptor transactivation activity

The mineralocorticoid receptor (MR) binds aldosterone, but also glucocorticoid hormones (corticosterone in rodents, cortisol in humans), which largely prevail in the plasma. To prevent permanent and maximal occupancy of MR by glucocorticoid hormones in aldosterone-target cells, specific effects of aldosterone require metabolism of glucocorticoid hormones into 11-dehydroderivatives by 11-beta hydroxysteroid dehydrogenase (11-HSD2). We analyzed the effect of corticosterone or 11-dehydrocorticosterone (11-DHC) on the transactivation activity of the MR, transiently expressed in a new renal cell line expressing 11-HSD2. We show that, because of its metabolism by 11-HSD2, corticosterone is a poor activator of MR transactivation, except at micromolar concentrations, where the enzyme is saturated. We also show that high micromolar concentrations of 11 DHC are required to activate the MR. The weak antagonist property of 11-DHC on aldosterone-induced hMR transactivations is also documented. Such partial agonist activity of 11-DHC is discussed in the light of its positioning in a three-dimensional model of the MR ligand-binding domain.     

Laparoscopic and percutaneous ablative techniques in the treatment of renal cell carcinoma

Widespread use of computed tomography, ultrasound, and magnetic resonance imaging has led to an increase in detection of relatively small renal masses, and approaches to managing them have evolved in the last two decades. Indications for nephron-sparing surgery have expanded, and minimally invasive procedures, which can confer advantages over open surgery, are now available. Ablative techniques offer a combination of nephron-sparing and minimally invasive approaches. Ablative techniques include cryoablation, radiofrequency ablation (RFA), and high-intensity focused ultrasound (HIFU). Cryoablation and RFA have been relatively safe. HIFU has been associated with serious side effects in animal models, and is not yet acceptable for use in humans. Ablative techniques require long-term studies to confirm lasting efficacy. The best modality for tumor targeting, monitoring of therapy, and follow-up is still under investigation. Debate exists regarding the best method for ensuring adequate intraoperative tumor cryoablation. For minimally invasive ablative measures to gain a place as nephron-sparing approaches, they should show both equivalent efficacy and reduced morbidity relative to those of open partial nephrectomy. These techniques should currently be reserved for selected patients and should be compared to the evolving modality of laparoscopic partial nephrectomy.     

Finding identifiable parameter combinations in nonlinear ODE models and the rational reparameterization of their input-output equations

When examining the structural identifiability properties of dynamic system models, some parameters can take on an infinite number of values and yet yield identical input-output data. These parameters and the model are then said to be unidentifiable. Finding identifiable combinations of parameters with which to reparameterize the model provides a means for quantitatively analyzing the model and computing solutions in terms of the combinations. In this paper, we revisit and explore the properties of an algorithm for finding identifiable parameter combinations using Gröbner Bases and prove useful theoretical properties of these parameter combinations. We prove a set of M algebraically independent identifiable parameter combinations can be found using this algorithm and that there exists a unique rational reparameterization of the input-output equations over these parameter combinations. We also demonstrate application of the procedure to a nonlinear biomodel.     

Deletion of the pseudoautosomal region and lack of sex-chromosome pairing at pachytene in two infertile men carrying an X;Y translocation

Two males with a 46,Y,der(X),t(X;Y)(p22.3;q11) complement were referred independently for evaluation of sterility with azoospermia. Both patients exhibited minimal symptomatology, characterized only by psychological disturbances. Study of X-chromosome breakpoints with pseudoautosomal probes 68B (DXYZ2 elements), 113D (locus DXYS15), and 19B (locus MIC2) indicated in both patients that at least 97% of the X pseudoautosomal sequences are lost. Hybridization with Xp22.3-specific probes DXS283, DXS284, and DXS31 shows that these loci are retained on the rearranged chromosome. Thus, the X-chromosome breakpoints are located close to the proximal boundary of the pseudoautosomal region, between MIC2 and DXS284.     

Composition and organization of tubulin isoforms reveals a variety of axonemal models

In the flagellum of mammalian spermatozoa, glutamylated and glycylated tubulin isoforms are detected according to longitudinal gradients and preferentially in axonemal doublets 1-5-6 and 3-8, respectively. This suggested a role for these tubulin isoforms in the regulation of flagellar beating. In the present work, using antibodies directed against various tubulin isoforms and quantitative immunogold analysis, we aimed at investigating whether the particular accessibility of tubulin isoforms in the mammalian sperm flagellum is restricted to this model of axoneme surrounded with periaxonemal structures or is also displayed in naked axonemes. In rodent lung ciliated cells, all studied tubulin isoforms are uniformly distributed in all axonemal microtubules with a unique deficiency of glutamylated tubulin in the transitional region. A similar distribution of tubulin isoforms is observed in cilia of Paramecium, except for a decreasing gradient of glutamylated tubulin labeling in the proximal part of axonemal microtubules. In the sea urchin sperm flagellum, predominant labeling of tyrosinated and detyrosinated tubulin in 1-5-6 and 3-8 doublets, respectively, were observed together with decreasing proximo-distal gradients of glutamylated and polyglycylated tubulin labeling and an increasing gradient of monoglycylated tubulin labeling. In flagella of Chlamydomonas, the glutamylated and glycylated tubulin isoforms are detected at low levels. Our results show a specific composition and organization of tubulin isoforms in different models of cilia and flagella, suggesting various models of functional organization and beating regulation of the axoneme.     

5-methylthioribose 1-phosphate: a product of partially purified, rat liver 5'-methylthioadenosine phosphorylase activity.

5'-Methylthioadenosine phosphorylase from rat liver has been purified 112-fold. A molecular weight of 90 000 for the enzyme was estimated from gel filtration on Sephadex G-150. The Km for 5'-methylthioadenosine was 4.7 . 10(-7) M, while the Km for phosphate was 2 . 10(-4) M. The products of the reaction were isolated and identified as adenine and 5-methylthioribose 1-phosphate. In addition to 5'-methylthioadenosine the nucleoside analogues 5'-ethylthioadenosine and 5'-n-propylthioadenosine also served as substrates for the enzyme. The 7-deaza analogue 5'-methylthiotubercidin was found to be an inhibitor of the reaction, but was inactive as a substrate.     

Hydroxysteroid dehydrogenase transformations of 5β-scymnol and identification of oxoscymnol transformation products by liquid chromatography-tandem mass spectroscopy

A new and sensitive high performance liquid chromatography (HPLC) separation procedure coupled with tandem mass spectroscopy (MS and MS(2)) detection was developed to identify for the first time the oxidation products of 5β-scymnol [(24R)-(+)-5β-cholestan-3α,7α,12α,24,26,27-hexol] catalysed by bacterial hydroxysteroid dehydrogenase (HSD) reactions in vitro. The authentic scymnol (MW 468) standard yielded a protonated molecular ion [M+H](+) at m/z 469 Da, and higher mass adduct ions attributed to [M+NH(4)](+) (m/z 486), [M+H+CH(3)OH](+) (m/z 501) and [M+H+CH(3)COOH](+) (m/z 530). (24R)-(+)-5β-Cholestan-3-one-7α,12α,24,26,27-pentol (3-oxoscymnol, m/z 467 Da, relative retention time (RRT)=0.89) was identified as the principle molecular species of scymnol in the reaction with 3α-HSD pure enzyme. [S](0.5) for the reaction of 3α-HSD with scymnol as substrate was 0.7292 mM. (24R)-(+)-5β-cholestan-7-one-3α,12α,24,26,27-pentol (7-oxoscymnol, m/z 467 Da, RRT=0.79) and (24R)-(+)-5β-cholestan-12-one-3α,7α,24,26,27-pentol (12-oxoscymnol, m/z 467 Da, RRT=0.81) were similarly identified as principle molecular species in the respective 7α-HSD and 12α-HSD reactions. Polarity of the oxoscymnol species was established as 7-oxoscymnol>12-oxoscymnol>3-oxoscymnol>scymnol (in order from most polar to least polar). Confirmation that 5β-scymnol is an oxidative substrate for steroid-metabolising enzymes was made possible by the use of sophisticated liquid chromatography-mass spectrometry (LC-MS) techniques that will likely provide the basis for further exploration of scymnol as a therapeutic compound.