Short-term stimulatory effect of Sertoli cell conditioned medium on Leydig cell steroidogenesis is not mediated by inhibin

Abstract Addition of concentrated rat Sertoli cell conditioned medium (rSCCM) to isolated Leydig cells from immature rats stimulated steroid production more than 13-fold within 4h. LH-stimulated steroidogenesis was not enhanced by addition of rSCCM. The biological activity of the concentrated rSCCM was higher after incubation of Sertoli cells with FSH, whereas FSH alone did not stimulate steroid production. This effect of rSCCM was not due to inhibin, since highly purified 32 kDa rat inhibin, in doses equivalent to those present in rSCCM, had no effect on steroidogenesis during the 4 h incubation period. Furthermore, inhibin could be separated from the Leydig cell stimulating factor by anion-exchange chromatography. These results indicate a short-term paracrine control of Leydig cell steroidogenesis by Sertoli cell derived factors, which differ from inhibin

The stimulatory effect of albumin on luteinizing hormone-stimulated Leydig cell steroid production depends on its fatty acid content and correlates with conformational changes

__Abstract__ The effects of purified albumin species and albumin fragments (0.2–1% w/v) on short-term (4 h) steroid secretion by immature rat Leydig cells, in the presence of a maximally stimulating dose of luteinizing hormone (LH), were investigated. Human albumin and the peptic fragment (comprising residues 1–387) enhanced pregnenolone production in isolated rat Leydig cells, whereas chicken albumin and the tryptic fragment (comprising residues 198–585) were not active. This stimulatory effect of human albumin and the peptic fragment correlated with the potential of these proteins to undergo a pH-dependent neutral-to-base transition as measured by circular dichroism. The tryptic fragment and chicken albumin did not have the potential to undergo such a transition. The pH-dependent conformational changes of albumin and fragments thereof occurred in parallel with a change in the binding affinity for testosterone and pregnenolone. The fatty acid oleic acid and the drug suramin, only when present in a molar ligand-to-albumin ratio equal to or higher than 2, inhibited the albumin-mediated stimulation of steroid production. These data show that the stimulatory effects of albumin species on LH-induced Leydig cell pregnenolone production depend on their fatty acid content and correlate with the potential of these molecules to undergo conformational changes. It is unknown via which mechanisms albumin exerts its stimulatory effect, but the LH action through the cyclic AMP pathway seems not to be affected

Stability of hepatitis C virus RNA during specimen handling and storage prior to NASBA amplification

The influence of different anticoagulants and pre-amplification storage conditions on the stability of hepatitis C virus (HCV)-RNA, as detected by the quantitative HCV NASBA assay (NASBA-QT), was studied. The HCV-RNA load remained stable for at least 15 months when serum or plasma samples (EDTA and heparin) were directly frozen at -70 degrees C in lysis buffer. At 4 degrees C, the HCV-RNA load in serum or plasma stored with lysis buffer did not decline for at least 14 days. At 30 degrees C, however, the load declined significantly after 7 days. When clotted, whole blood was stored at 4 degrees C, the HCV-RNA load was stable for 72 h. However, when EDTA-anticoagulated whole blood was stored at 4 degrees C, the HCV-RNA load declined significantly after 48 h. In paired plasma and serum samples at baseline the HCV-RNA levels were similar. Heparin did not influence the efficiency of the HCV NASBA-QT assay. Clotted blood as well as EDTA or heparin anticoagulated blood can be used for quantifying HCV-RNA using the NASBA-QT assay. Blood samples should be stored at 4 degrees C after collection and serum or plasma separated within 24 h. Preferably, after separation, samples should be frozen in lysis buffer at -70 degrees C until NASBA-QT analysi

The human thyroglobulin gene: a polymorphic marker localized distal to C-MYC on chromosome 8 band q24

The human thyroglobulin (Tg) gene is localized to chromosome 8 and regionally to band q24 as shown independently by both in situ hybridization techniques and Southern blot analysis of human-rodent somatic cell hybrids. Analysis of hybrids derived from a Burkitt lymphoma, with a translocation breakpoint in the oncogene c-myc, shows that the Tg gene is located distal from c-myc, towards the telomere of the long arm of chromosome 8. The finding of two high frequency restriction fragment length polymorphisms (RFLPs) in the 5' part of the Tg gene results in heterozygosity for at least one marker at chromosome 8, band q24, in 50% of a Caucasian population. These RFLPs cannot only be used for the study of inborn errors in Tg synthesis but also for linkage studies in the telomeric region of chromosome 8