Staging of rectal cancer by double-contrast MR imaging using the rectally administered superparamagnetic iron oxide contrast agent ferristene and IV gadodiamide injection: results of a multicenter phase II trial.

The aim of this study was to assess the accuracy of double-contrast magnetic resonance imaging (MRI) with rectal application of the superparamagnetic iron oxide contrast agent (SPIO) ferristene and IV gadodiamide for preoperative staging of rectal cancer. In a randomized phase II dose-ranging trial, 113 patients were studied preoperatively with one of four different formulations of ferristene (Abdoscan) as an enema before MRI. T1-weighted spin-echo (T1w SE) and T2w turbo spin-echo (TSE) single-contrast images were obtained as well as T1w SE and gradient-echo (GRE) double-contrast images after IV gadodiamide injection (Omniscan).

Molecular principles of Oct2-mediated gene activation in B cells.

The octamer motif is a crucial regulatory element for immunoglobulin promoter and enhancer function. We have investigated the molecular mechanisms that underlie octamer-mediated gene activation in B cells. This B cell-specific transcriptional regulation is subject to a novel type of regulatory mechanism.

Functional differences between the Oct2 transactivation domains determine the transactivation potential of individual Oct2 isoforms.

The lymphocyte specific transcription factor Oct2 is involved in mediating the B-cell specific transcriptional activity of the octamer motif. Mutational analyses in the context of the complete Oct2 protein had indicated that Oct2 contains two transactivation domains. These two domains appeared to be redundant for activation from a promoter proximal position, whereas stimulation from a remote enhancer position specifically required the C-terminal transactivation domain and an additional B-cell restricted activity.

The POU domains of the Oct1 and Oct2 transcription factors mediate specific interaction with TBP.

We had previously shown that the ubiquitous Oct1 and the lymphoid-specific Oct2 transcription factors stimulate transcription at the level of stable preinitiation complex formation. We have therefore investigated whether the octamer binding proteins might physically interact with TBP, the TATA box binding protein component of the TFIID factor. By using several different experimental systems we show that TBP efficiently associates with Oct1 and Oct2.

Differential transactivation potential of Oct1 and Oct2 is determined by additional B cell-specific activities.

Cell type-specific transcriptional regulation is generally believed to be mediated by sequence-specific transcription factors that are specifically present in the corresponding cells. The interaction of the lymphoid-specific Oct2 transcription factor has been thought to be responsible for the B cell-specific activity of octamer-containing promoter and enhancer elements. Here we show that physiological concentrations of Oct2 do not suffice to generate octamer-dependent promoter activity in non-B cell lines.

Analysis of transcriptional stimulation by recombinant Oct proteins in a cell-free system.

The transactivation potential of several isoforms of the lymphoid-specific transcription factor Oct2 has been analyzed using in vitro transcription. Oct2 can stimulate transcription in B-cell nuclear extracts and in HeLa nuclear extracts depleted of the ubiquitous factor Oct1 by wheat germ lectin affinity chromatography. Activity is observed from both natural and synthetic promoters containing single or multiple copies of the octamer motif ATGCAAAT.

Oct2 transactivation from a remote enhancer position requires a B-cell-restricted activity.

Previous cotransfection experiments had demonstrated that ectopic expression of the lymphocyte-specific transcription factor Oct2 could efficiently activate a promoter containing an octamer motif. Oct2 expression was unable to stimulate a multimerized octamer enhancer element in HeLa cells, however. We have tested a variety of Oct2 isoforms generated by alternative splicing for the capability to activate an octamer enhancer in nonlymphoid cells and a B-cell line.

Functional analysis of defined mutations in the immunoglobulin heavy-chain enhancer in transgenic mice.

We have analyzed the effect of defined mutations in the mouse immunoglobulin heavy-chain enhancer after introduction into the germline of transgenic mice. We have tested a mutation of the enhancer octamer motif, a double mutation of the octamer motif and the microB-site, and a triple mutation in the microE2, microE3 and microE4-sites. All constructs are expressed in the spleen of transgenic mice.

Multiple Oct2 isoforms are generated by alternative splicing.

The interaction of the Oct2 transcription factor with the cognate octamer motif ATGCAAAT is a critical determinant of the lymphoid-specific expression of immunoglobulin genes. Ectopic expression of cloned Oct2 cDNA was shown to be sufficient to reconstitute at least some aspects of this regulation in non-lymphoid cells. We describe the isolation and characterization of multiple cDNAs encoding mouse Oct2 from a mature B-cell line and we show that a variety of isoforms of this transcription factor is generated from a single gene by an alternative splicing mechanism.

[A low-cost localization technique for high-dose-rate afterloading applicators].

For radiation safety control radiotherapy today needs a method to check the correct position of a HDR-gynecological applicator before afterloading treatment. At the university clinic in Essen, West Germany, a surgical c-X-ray plant was used for the construction of an orthogonal X-ray-photograph plant, which combines illumination and photographs as localisation technique.