[Survival analysis of adjustable continence therapy device (ACT®/proACT®): a new message for patients]. / Étude de survie des ballonnets ACT®/proACT® : un nouveau message pour les patients.

INTRODUCTION: The main purpose was to assess the failure free survival of adjustable continence therapy ACT®/proACT® after continence was obtained and to seek factors influencing it. MATERIAL AND METHODS: Retrospective, single-center survival study of peri-urethral balloons implanted between 2007 and 2014. Efficacy was defined by the wearing of 0 or 1 safety pad per day. The primary end point was time to failure estimated from a survival curve (Kaplan-Meier). Factors that could influence failure free survival were: sex, age, radiotherapy, diabetes, number of pad before surgery, number of balloon inflation, early complications, mixed urinary incontinence and previous ACT®/proACT® placement. They were analyzed in a COX regression. RESULTS: Of the 82 peri-urethral balloons placed, 41 were effective in 36 patients. The failure free survival was 50 % at 60 months. Radiotherapy, diabetes and previous peri-urethral balloon placement appeared to significantly decrease survival (P=0.031;P=0.025;P=0.029, respectively). Fifteen peri-urethral balloons were still effective at the last follow-up, one was lost to follow-up and 25 required re-intervention for loss of efficacy. The main cause of efficacy loss was system leakage. Fifty-two percent of peri-urethral balloons that became ineffective were replaced by new peri-urethral balloons and 28% by an artificial urinary sphincter. CONCLUSION: Patients who became continent with adjustable continence therapy (ACT®/proACT®) had a 50 % new surgery probability at 5 years for a loss of efficacy. Radiotherapy seems to be the main risk factor of the efficacy loss. LEVEL OF EVIDENCE: IV.

Anatomical description of the umbilical arteries and impact of their ligation on pelvic and perineal vascular supply after cystectomy in women.

OBJECTIVE: In radical cystectomy, the surgeon generally ligates the umbilical artery at its origin. This artery may give rise to several arteries that supply the sexual organs. Our aim was to evaluate pelvic and perineal devascularisation in women after total cystectomy. PATIENTS AND METHODS: We carried out a prospective anatomical and radiological study. We performed bilateral pelvic dissections of fresh adult female cadavers to identify the dividing branches of the umbilical artery. In parallel, we examined and compared the pre- and postoperative imaging investigations [magnetic resonance imaging (MRI) angiography] in patients undergoing cystectomy for benign disease to quantify the loss of pelvic vascularisation on the postoperative images by identifying the occluded arteries. RESULTS: The anatomical study together with the radiological study visualised 35 umbilical arteries (n = 70) with their branching patterns and collateral arteries. The uterine artery originated from the umbilical artery in more than 75% of cases (n = 54) of the internal pudendal artery in 34% (n = 24) and the vaginal artery in 43% (n = 30). The postoperative MRI angiograms showed pelvic devascularisation in four patients. Devascularisation was dependent on the level of surgical ligation. In the four patients with loss of pelvic vascular supply, the umbilical artery had been ligated at its origin. CONCLUSION: The umbilical artery gives rise to various branches that supply the pelvis and perineum. If the surgeon ligates the umbilical artery at its origin during total cystectomy, there is a significant risk of pelvic and perineal devascularisation.

[Assessment of the learning curves for intravesical adenoma morcellation using Piranha© device during endoscopic enucleation]. / Analyse de la courbe d'apprentissage de la morcellation intravésicale réalisée avec le système Piranha© au cours de l'énucléation endoscopique.

INTRODUCTION: Morcellation of intravesical adenoma (MIA) is an important part of the endoscopic enucleation procedure. The aim of this study was to analyse the learning curve of the MIA during endoscopic enucleation of the prostate. MATERIAL: We conducted a prospective study of the first 90 patients treated by endoscopic enucleation of the prostate by a single surgeon without previous experience of MIA. The population was divided into 3 consecutive groups of 30 patients. MIA was performed with the morcellator Pinranha (Wolf) and disposable blades (Vmax©). The criteria selected to assess the progress of MIA over time were: duration of MIA (min), the intraoperative complications encountered during MIA and weight morcelleted tissue. The efficacy of MIA was assessed with the ratio weight specimen/MIA duration (min/g) over time. RESULTS: The three groups were comparable in terms of age, ASA score of prostate volume. A significant decrease in the duration of MIA was found between groups 1 and 2 (12 versus 5.5min, P<0.0001), to reach a plateau in the group 3 (3min). A significant increase in the efficiency of MIA was found between group 1 and 2 (5.5 versus 11g/min, P<0.0001), to reach a plateau in the group 3 (20g/min). Bladder injuries were limited (7.7%), superficial and encountered in the early learning phase. CONCLUSION: In our experience, the MIA required a learning curve estimated between 30 and 60 procedures. LEVEL OF EVIDENCE: IV.

What risk of prostate cancer led urologist to recommend prostate biopsies?

OBJECTIVE: The aim of this study was to estimate the risk of prostate cancer that led urologists to perform prostate biopsies. PATIENTS AND METHODS: Eight hundred and eight patients had prostate biopsies in 5 tertiary centres in 2010. Following data were collected: age, PSA, DRE, prostate volume, negative prior prostate biopsy and estimated life expectancy (> or <10 years). The risk of prostate cancer was calculated by validated nomogram of PCPT-CRC and SWOP-PRI and correlated with pathological biopsy results. RESULTS: In final analysis, 625 patients were included, 568 (90.9%) had a life expectancy greater than 10 years. Prostate cancer was found in 291 (46.6%) cases. These patients were older (66.7 ± 6.8 vs 64.3 ± 5.6 years, P < 0.001), had higher PSA values (10 ± 7.9 vs 7.7 ± 4.3 ng/mL, P < 0.0001) and the prostate volume decreased (43.8 ± 19.8 vs 51.3 ± 20.7 mL, P < 0.0001) compared with healthy subjects. Digital Rectal Examination was more frequently suspicious in the group of patients with prostate cancer (43.6% vs 18.9%, P < 0.0001). Risk of prostate cancer estimated was 50.6 ± 14% for PCPT-CRC without ATCD, 56.2 ± 12.8% with PCPT-CRC ATCD and 31.2 ± 17.3% for SWOP-PRI. The likelihood of high-risk prostate cancer was 22.4 ± 16.9% with the PCPT-CRC, and 14.8 ± 18.2% with SWOP-PRI. CONCLUSION: This study showed that urologists performed prostate biopsies when the risk of cancer was high.

[XPS Greenlight photoselective vaporization for benign prostatic hyperplasia: analysis of the learning curve and contribution of transrectal ultrasound monitoring]. / Traitement de l'hyperplasie bénigne de prostate par photovaporisation au laser Greenlight XPS: analyse de la courbe d'apprentissage et apport de l'échographie endorectale peropératoire.

INTRODUCTION: The aim of this study was to analyze the XPS laser learning curve of one single surgeon with no previous experience of PVP and the impact of the use of reel time transrectal ultrasound (TRUS) monitoring. MATERIALS AND METHODS: Retrospective analysis of the first 100 patients: group 1 (1st-49th patient without TRUS) and group 2 (50th-100th with TRUS). The learning curve was analyzed through technical variables: vaporization time/intervention time (VT/IT) (%), energy delivered (J)/prostate volume (J/mL) and delivered energy (J/s or Watt), peroperative conversion into monopolar transurethral resection, postoperative complication, duration of catheterization and hospitalization and evolution of International Prostate Symptom Score (IPSS), PSA level, prostate residual volume and Qmax. Relationships between variables were evaluated by analysing the covariance (R 2 software. 14.2). RESULTS: A significant increase in VT/IT (P=0.0001) and the energy delivered per mL prostate (P=0.043) was reported in group 1. The average energy delivered per second was significantly higher in group 2 (P=0.0016). No difference was observed in terms of intra- or postoperative complication and catheterization time. The duration of hospitalization was significantly shorter in group 2 (P=0.03). The use of TRUS was associated with a gain of energy delivered by prostate volume at the end of learning curve (P=0.018). Prostate residual volume was significantly lower in the group 2 (P=0.0004). CONCLUSION: In our experience, 50 procedures are required to achieve the learning curve of PVP. The use of reel time TRUS would increase the energy delivered by prostate volume.

[The management of prostate cancer: a retrospective chart review in 808 French men undergoing biopsy]. / Prise en charge du cancer de la prostate: analyse rétrospective de 808 hommes biopsiés en France.

OBJECTIVE: We explored the characteristics of a sample of men who had undergone a biopsy in clinical practice in France and evaluated initial treatment choice in men with a positive biopsy. METHODS: This was a multi-centre, retrospective chart review including men who had undergone a biopsy in France. Clinical variables were collected using an electronic data capture system. RESULTS: Eight hundred and eight men were included; 632 men (78%) had an initial biopsy and 176 men (22%) had one or more repeat biopsy. The mean age was 64 years and 9% of men were 75 years or more. The mean (median) PSA was 11.6 (7.0) ng/mL; 25% of men had a PSA greater than 10 ng/mL. Twenty-eight percent of men had a suspicious DRE. A total of 52% of men had a positive initial and 26% a positive repeat biopsy. One hundred and eleven patients (34%) had low-risk PCa (stage T1c-2a, PSA<10 ng/mL, Gleason sum<7) and 195 (59%) were at intermediate/high risk of disease progression. The most common treatment was radical therapy (54% of patients), even in men with low-risk PCa (40% of patients). A total of 38% of low-risk patients chose active surveillance. CONCLUSIONS: The French biopsy sample appeared to be at a relatively high risk of having PCa at initial biopsy. Radical therapy was the most common treatment choice in men with a positive biopsy. In patients with low-risk PCa, radical therapy and active surveillance were used most often and to the same extent.

[Greenlight(®) photoselective vaporisation for benign prostatic hyperplasia: a systematic review]. / Traitement de l'hyperplasie bénigne de prostate par photovaporisation au laser Greenlight(®) : analyse de la littérature.

INTRODUCTION: Transurethral resection of the prostate (TURP) is the most common surgical procedure in urology and remains the gold standard treatment of complicated benign prostatic hyperplasia or refractory to medical treatment. Routinely used since the 2000s, prostate photoselective vaporization (PVP) with Greenlight(®) laser has been developed to improve the safety of hemostasis in elderly patients and/or with high surgical risk. The purpose of this study was to review the results of PVP from the international literature. MATERIAL AND METHODS: [corrected] A systematic review of the literature on the research base Pubmed (http://www.ncbi.nlm.nih.gov/) was performed using the keywords benign prostatic hyperplasia; greenlight; photovaporisation; Laser; IPSS score; endoscopicsurgery; morbidity; complication. Prospective and retrospective studies in English and French were selected from its first use in 1998. Finally, we looked for studies that reported at least one of the following items: surgical technique; operative data; complications; anatomical and functional results and/or direct comparison between PVP and TURP. RESULTS: Regardless the PVP technique used to treat adenoma and identify the limits of the prostatic capsule, some parameters are well defined (sweepspeed, angle and distance of the fiber with the tissue) but others are still debated (number of joules per volume, when do we have to stop the PVP) and are reported in a heterogeneous manner due to the different generators. Versus TURP, PVP would offer the same functional results in the medium term but with a lower risk of per- and postoperative bleeding. The study of the risk of erectile dysfunction (ED) after PVP is made difficult due to the heterogeneity of DE assessment and study populations. However, PVP does not seem associated with an increased risk of ED versus TURP. The lack of histological material should lead to preoperative individual screening of prostate. The economy generated by PVP regarding the decrease in average length of stay has been clearly identified in Australia, Canada, Switzerland and USA. Studies will be published soon on French economic model. CONCLUSION: PVP with Greenlight(®) laser appears to be a safe and effective technique. With the new generator XPS, the PVP technique reaches maturity. Its development will certainly lead to a long-term evaluation with high levels of evidence based.

[Should we consider a complementary treatment after a renal colic drained by an ureteral stent?]. / Faut-il envisager un traitement complémentaire après une colique néphrétique drainée par une sonde JJ ?

PURPOSE: The aim of the study was to evaluate if only ureteral stent removing after complicated renal colic (RC) could prevent from complementary treatment (shock-wawe lithortripsy or ureteroscopy). PATIENTS AND METHODS: Data from 95 patients, 39 women and 56 men, who had an ureteral stent for complicated RC from 2005 to 2010 were retrospectively collected. Mean age was 46.4 ± 17.2 years. After the initial management, another hospitalization was organized where patients had ureteral stent removing under local anesthesia, then an abdominal CT-scan without injection and complementary treatment of ureteral stones (none or ESWL or ureteroscopy). Parameters studied were age, sex, stone size, location of calcul. Quantitative values were compared with Student's t test. Qualitative values were compared with the Chi(2). P<0.05 was considered statistically significant. RESULTS: Mean duration between the two hospitalizations were 1.58 ± 1.84 months. Sixty-one patients (64.2%) had no more urolithiasis. In these patients, mean size of urolithiasis was 5.85 ± 2.33 mm. Location of urolithiasis in distal, mild and proximal ureter was 77%, 3% and 20% respectively. Thirty-four patients (35.8%) had persistant lithiasis after CT-scan. Location of stone in distal, mild and proximal ureter was 17.5%, 5.8% and 76.7% respectively. CONCLUSION: After management of complicated renal colic by ureteral stent, 64% of patients had spontaneous elimination of stones after removing of ureteral stent, especially in women and pelvic ureter.

[Hexaminolevulinate fluorescence cystoscopy in 2009]. / Le point sur les indications de l'Hexvix en 2009.

Fluorescence cystoscopy improves the detection of non-muscle-invasive bladder cancer, particularly carcinoma in situ, and reduces recurrence. The technique is well tolerated with few side effects. Guidelines recommend fluorescence cystoscopy in multifocal tumors, tumors >3cm, early recurrence, High grade cytology, follow-up of high-risk bladder cancer (T1G3 and CIS).

[Long-term outcome of patients with renal transplant and neural tube defect]. / Suivi au long terme des patients transplantés rénaux ayant un dysraphisme spinal.

PURPOSE: To evaluate the long term outcome of renal transplant in patients with a neural tube defect causing voiding dysfunctions. PATIENT AND METHODS: Between 1993 and 2010, 18 cadaveric renal transplants were performed in 16 patients (5 females and 11 males) older than 15 years with a neural tube defect and voiding dysfunction. RESULTS: The patients had dialysis since the mean age of 27.4 and have been transplanted at the mean age of 32.2. The survival rate of the first kidney transplant was 93.75% at 1 year and 63.3% at 5 and 10 years respectively. With a mean follow-up of 6.67 years, 11 out of 16 first transplants remained functional (68.75%) The median survival of the first transplants was 13.52 years. At the end of the follow-up, 13 out of 18 transplants were still functional (72.2%). The mean serum creatinine level was 123.9 micromol/l with a mean glomerular filtration rate estimated by the simplified MDRD formula of 67 ml/min for the 13 still functional transplants. Before transplantation, 66% of patients had a neuro-urologic assessment versus 100% thereafter. CONCLUSION: Renal transplantation in patients with neural tube defect is feasible without surgical particularities to those of other renal failure causes. These type of patients represented less than 1% of the followed cohort with an average graft survival rate of 63.3% at five and 10 years. The median survival time of the first graft was 13.52 years.

Sustained survival of human hepatocytes in mice: A model for in vivo infection with human hepatitis B and hepatitis delta viruses.

Persistence of hepatocytes transplanted into the same or related species has been established. The long-term engraftment of human hepatocytes into rodents would be useful for the study of human viral hepatitis, where it might allow the species, technical and size limitations of the current animal models to be overcome. Although transgenic mice expressing the hepatitis B virus (HBV) genome produce infectious virus in their serum, the viral life cycle is not complete, in that the early stages of viral binding and entry into hepatocytes and production of an episomal transcriptional DNA template do not occur. As for hepatitis delta virus (HDV), another cause of liver disease, no effective therapy exists to eradicate infection, and it remains resistant even to recent regimens that have considerably changed the treatment of HBV (ref. 13). Here, we demonstrate long-term engraftment of primary human hepatocytes transplanted in a matrix under the kidney capsule of mice with administration of an agonistic antibody against c-Met. These mice were susceptible to HBV infection and completion of the viral life cycle. In addition, we demonstrate super-infection of the HBV-infected mice with HDV. Our results describe a new xenotransplant model that allows study of multiple aspects of human hepatitis viral infections, and may enhance studies of human liver diseases.

Preferential interaction of human immunodeficiency virus reverse transcriptase with two regions of primer tRNA(Lys) as evidenced by footprinting studies and inhibition with synthetic oligoribonucleotides.

Primer tRNA regions involved in the interactions between human immunodeficiency virus reverse transcriptase (HIV RT) and tRNA(Lys) were studied by digestion of primer with pancreatic ribonuclease in the presence or absence of HIV RT. The acceptor stem of tRNA(Lys) is not noticeably protected against nuclease action in the presence of HIV RT, while this enzyme clearly protects part of the anticodon and dihydrouridine loops of tRNA(Lys). The acceptor stem of primer tRNA was digested by RNase A only in the presence of the retroviral enzyme, suggesting a partial destabilization of this region by the HIV RT. Synthetic oligoribonucleotides, corresponding to the anticodon and the dihydrouridine loops, inhibited strongly reverse transcription, confirming the strong interaction of these tRNA regions with the enzyme.

Interactions with tRNA(Lys) induce important structural changes in human immunodeficiency virus reverse transcriptase.

Retroviral RNA-dependent DNA polymerase (reverse transcriptase or RT) uses the 3'OH end of a cellular tRNA as primer to initiate DNA synthesis. Previous work with avian retrovirus has shown that reverse transcriptase is implicated in the selection of cellular virion-encapsidated tRNAs and has shown that the primer tRNA is positioned on the primer binding site near the 5' end of the viral RNA. These mechanisms support the idea that the retroviral polymerase should form complexes with primer tRNA and the specific encapsidated ones. The genomic sequence of human immunodeficiency virus (HIV) allows the prediction that tRNA(Lys3) is the natural primer. In this article we show, using the mobility shift assay, that recombinant HIV reverse transcriptase is able to form a complex with bovine tRNA(Lys.) By fluorescence studies and alpha-chymotrypsin analysis we have observed a modification of the enzyme conformation when reverse transcriptase is bound to the putative primer tRNA. This structural change is specific for tRNA(Lys) although the retroviral polymerase is able to interact with other tRNAs.

Inhibition of the p66/p51 form of human immunodeficiency virus reverse transcriptase by tRNA(Lys).

Human immunodeficiency virus (HIV) reverse transcriptase (RT) uses host tRNA(Lys) partially annealed to the primer binding site (PBS) as primer for the initiation of cDNA synthesis. When assaying cDNA synthesis with a template-primer complex formed by an RNA fragment carrying the PBS site and bovine tRNA(Lys) we noticed that an excess of primer tRNA inhibited strongly the DNA polymerase activity of a recombinant HIV RT (p66-p51 heterodimeric form) produced in transformed yeast cells. The same inhibitory effect was observed with animal DNA polymerase alpha, while avian retrovirus RT was neither affected by tRNA(Lys) nor by its specific primer tRNA(Trp). Although the strongest inhibition was observed with tRNA(Lys), other tRNas like tRNA(Phe) and tRNA(Trp) inhibited also the HIV RT, whereas tRNAs specific for valine, proline and glycine had no effect on enzyme activity. Digestion of tRNA(Lys) with pancreatic RNase abolished the inhibition; on the other hand T1 RNase digestion had no effect on the inhibition suggesting a role of the anticodon region in this effect. The 12- and 14-mers corresponding to the anticodon regions of the three bovine tRNA(Lys) isoacceptors inhibited RT activity, indicating that at least an important part of the inhibitory effect could be ascribed to this tRNA region. A strong stimulation of DNA polymerase activity was observed when the effect of tRNA(Lys) was assayed on a recombinant HIV reverse transcriptase produced in a protease deficient yeast strain, which leads to the production of an active p66 enzyme. The same tRNAs that inhibited strongly the heterodimeric form stimulated the p66 form of HIV reverse transcriptase. The results suggest that although both enzymatic forms are able to interact with tRNA(Lys) the topography, as well as the functional implications of the interaction between the precursor and the mature form of HIV reverse transcriptase with the tRNA(Lys) primer, are different.

Identification of two steroid-responsive promoters of different strength controlled by the same estrogen-responsive element in the 5'-end region of the Xenopus laevis vitellogenin gene A1.

A structural and functional analysis of the 5'-end region of the Xenopus laevis vitellogenin gene A1 revealed two transcription initiation sites located 1.8 kilobases apart. A RNA polymerase II binding assay indicates that both promoters form initiation complexes efficiently. In vitro, using a transcription assay derived from a HeLa whole-cell extract, the upstream promoter is more than 10-fold stronger than the downstream one. In contrast, both promoters have a similar strength in a HeLa nuclear extract. In vivo, that is in estrogen-stimulated hepatocytes, it is the downstream promoter homologous to the one used by the other members of the vitellogenin gene family, which is 50-fold stronger than the upstream promoter. Thus, if functional vitellogenin mRNA results from this latter activity, it would contribute less than 1% to the synthesis of vitellogenin by fully induced Xenopus hepatocytes expressing the four vitellogenin genes. In contrast, both gene A1 promoters are silent in uninduced hepatocytes. Transfection experiments using the Xenopus cell line B3.2 in which estrogen-responsiveness has been introduced reveal that the strong downstream promoter is controlled by an estrogen responsive element (ERE) located 330 bp upstream of it. The upstream promoter can also be controlled by the same ERE. Since the region comprising the upstream promoter is flanked by a 200 base pair long inverted repeat with stretches of homology to other regions of the X. laevis genome, we speculate that it might have been inserted upstream of the vitellogenin gene A1 by a recombination event and consequently brought under control of the ERE lying 1.5 kilobases downstream.

Immuno-electron microscopic identification of human estrogen receptor-DNA complexes at the estrogen-responsive element and in the first intron of a Xenopus vitellogenin gene.

Using an extract of nuclei from the estrogen-responsive human breast cancer cell line MCF-7, protein-DNA complexes were assembled in vitro at the 5' end of the Xenopus laevis vitellogenin gene B2 that is normally expressed in liver after estrogen induction. The complexes formed were analyzed by electron microscopy after labeling by the indirect colloidal gold immunological method using a monoclonal antibody specific for the human estrogen receptor. As identified by its interaction with protein A-gold, the antibody was found linked to two protein-DNA complexes, the first localized at the estrogen responsive element of the gene and the second in intron I, thus proving a direct participation of the receptor in these two complexes. The procedure used allows the visualization and rapid localization of specific transcription factors bound in vitro to a promoter or any other gene region.

Expression of human estrogen receptor mutants in Xenopus oocytes: correlation between transcriptional activity and ability to form protein-DNA complexes.

The human estrogen receptor (hER) is a trans-acting regulatory protein composed of a series of discrete functional domains. We have microinjected an hER expression vector (HEO) into Xenopus oocyte nuclei and demonstrate, using Western blot assay, that the hER is synthesized. When nuclear extracts from oocytes were prepared and incubated in the presence of a 2.7 kb DNA fragment comprising the 5' end of the vitellogenin gene B2, formation of estrogen-dependent complexes could be visualized by electron microscopy over the estrogen responsive element (ERE). Of crucial importance is the observation that the complex formation is inhibited by the estrogen antagonist tamoxifen, is restored by the addition of the hormone and does not take place with extracts from control oocytes injected with the expression vector lacking the sequences encoding the receptor. The presence of the biologically active hER is confirmed in co-injection experiments, in which HEO is co-introduced with a CAT reporter gene under the control of a vitellogenin promoter containing or lacking the ERE. CAT assays and primer extensions analyses reveal that both the receptor and the ERE are essential for estrogen induced stimulation of transcription. The same approach was used to analyze selective hER mutants. We find that the DNA binding domain (region C) is essential for protein--DNA complex formation at the ERE but is not sufficient by itself to activate transcription from the reporter gene. In addition to region C, both the hormone binding (region E) and amino terminal (region A/B) domains are needed for an efficient transcription activation.(ABSTRACT TRUNCATED AT 250 WORDS)

Vaccinia virus produces late mRNAs by discontinuous synthesis.

We describe the unusual structure of a vaccinia virus late mRNA. In these molecules, the protein-coding sequences of a major late structural polypeptide are preceded by long leader RNAs, which in some cases are thousands of nucleotides long. These sequences map to different regions of the viral genome and in one instance are separated from the late gene by more than 100 kb of DNA. Moreover, the leader sequences map either upstream or downstream of the late gene, are transcribed from either DNA strand, and are fused to the late gene coding sequence via a poly(A) stretch. This demonstrates that vaccinia virus produces late mRNAs by tagging the protein-coding sequences onto the 3' end of other RNAs.

Electron microscopic visualization of protein-DNA interactions at the estrogen responsive element and in the first intron of the Xenopus laevis vitellogenin gene.

Stable protein-DNA complexes can be assembled in vitro at the 5' end of Xenopus laevis vitellogenin genes using extracts of nuclei from estrogen-induced frog liver and visualized by electron microscopy. Complexes at the three following sites can be identified on the gene B2: the transcription initiation site, the estrogen responsive element (ERE) and in the first intron. The complex at the transcription initiation site is stabilized by dinucleotides and thus represents a ternary transcription complex. The formation of the complexes at the two other sites is enhanced by estrogen and is reduced by tamoxifen, an antagonist of estrogen, while this latter effect is reversed by adding an excess of hormone. No sequence homology is apparent between the site containing the ERE and the binding site in intron I and functional tests in MCF-7 cells suggest that these two sites are not equivalent. Finally, we made use of previously characterized deletion mutants of the 5' flanking region of the gene B1, a close relative of the gene B2, to demonstrate that the 13-bp palindromic core element of the ERE is involved in the formation of the complexes observed upstream of the transcription initiation site.