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Biomedical subjects

J F Jansen

Publications and source records attributed to J F Jansen.

8 recordsLinked to original sources
PubMed2001

Stereotactic breast biopsy: a six-year surgical experience.

A retrospective review was done of all stereotactic breast biopsies performed at the Central Baptist Hospital Breast Center from February 1994 through December 1999. A total of 1,080 biopsies were performed in 1,026 patients, all by surgeons working independently. Masses were biopsied in 54% and calcifications in 40%. Eighteen percent of biopsies were malignant. The most common benign diagnosis was fibrocystic disease (72%), followed by fibroadenoma (19%), lymph node (2%), and papilloma (2%). The most common malignant diagnosis was invasive ductal carcinoma (40%) followed by ductal carcinoma in situ (32%) and mixed invasive and in situ ductal carcinoma (19%). A prebiopsy BI-RADS mammographic Category III was associated with a 2% incidence of malignancy; Category IV--17%; Category V--90%. Atypical ductal hyperplasia on stereotactic biopsy was upgraded to a malignant diagnosis after reexcision in 19% of the cases. The false-negative rate was 0.4% (sensitivity 99%) and the complication rate was 3%, mostly related to bleeding. Stereotactic biopsy is a safe and accurate technique for the minimally-invasive diagnosis of abnormal mammograms.

Adult↗
PubMed2000

The Mad1-Sin3B interaction involves a novel helical fold.

Sin3A or Sin3B are components of a corepressor complex that mediates repression by transcription factors such as the helix-loop-helix proteins Mad and Mxi. Members of the Mad/Mxi family of repressors play important roles in the transition between proliferation and differentiation by down-regulating the expression of genes that are activated by the proto-oncogene product Myc. Here, we report the solution structure of the second paired amphipathic helix (PAH) domain (PAH2) of Sin3B in complex with a peptide comprising the N-terminal region of Mad1. This complex exhibits a novel interaction fold for which we propose the name 'wedged helical bundle'. Four alpha-helices of PAH2 form a hydrophobic cleft that accommodates an amphipathic Mad1 alpha-helix. Our data further show that, upon binding Mad1, secondary structure elements of PAH2 are stabilized. The PAH2-Mad1 structure provides the basis for determining the principles of protein interaction and selectivity involving PAH domains.

Amino Acid Sequence↗
PubMed1995

Synthesis and cytotoxicity of novel lignans.

In this study the syntheses of 11 novel lignans are described. Their cytotoxicities are studied in GLC4, a human small cell lung carcinoma cell line, using the microculture tetrazolium (MTT) assay. Ten of these compounds were substituted with a menthyloxy group on the 5-position of the lactone. These compounds can easily be prepared in (novel) 'one-pot', three- or four-step syntheses. In addition, methods for controlling the stereogenic centers are described. Furthermore, five naturally occurring podophyllotoxin-related compounds were tested. The cytotoxicities of all lignan compounds, and of three non-lignan intermediates originating from the syntheses, were compared with the clinically applied anticancer agents etoposide, teniposide, and cisplatin. Most compounds showed moderate to high activities against GLC4, and two of the compounds containing a menthyloxy group showed activities comparable to the reference cytotoxic agents.

Antineoplastic Agents↗
PubMed1995

Cytokeratin positivity in fine-needle aspirates of melanomas and sarcomas.

Cytokeratin (CK) positivity has been considered a specific marker for epithelial differentiation in cytologic specimens. After observing CK reactivity in fine-needle aspirate (FNA) specimens of melanoma and sarcoma, a retrospective study of melanomas and sarcomas was undertaken to investigate the frequency of anomalous CK staining in these neoplasms. Cell block sections and/or restained smears from 36 melanomas and sarcomas were retrospectively stained for CK. An appropriate internal positive control (HMB-45), S100 protein, or vimentin) was also used to insure antigen preservation. Of the smears from 19 melanomas, five revealed focal strong CK positivity of neoplastic cells, two cases showed faint or equivocal staining, 11 cases were negative for CK, and one could not be interpreted due to inadequate controls. Of the smears from 14 sarcomas, two showed positivity for CK (one fibrosarcoma and one condrosarcoma), 11 were negative, and one had inadequate controls. The number of CK positive cells was less than that observed with the appropriate internal positive control antibodies. Destained Papanicolaou smears were superior to Diff-Quik smears for retrospective immunocytochemical stains. Cell block sections from four of the melanomas and one sarcoma demonstrated no aberrant staining. Since cytokeratin positivity occasionally is seen in nonepithelial neoplasms, its presence alone cannot be used to make a definitive diagnosis of carcinoma. Therefore, a panel of immunocytochemical stains should be utilized in diagnosis of FNA specimens.

Biopsy, Needle↗
PubMed1990

Radionuclide concentrations in the northern part of The Netherlands after the Chernobyl reactor accident.

Concentrations of radionuclides originating from the Chernobyl reactor accident were measured as a function of time in air, rainwater, grass, cow's milk, vegetables and dust by means of high-resolution gamma-ray spectroscopy. Special attention was paid to grass and milk originating from the same meadows. Also, milk of cows temporarily kept inside after the accident was monitored until a few days after their release from the stables. Activity ratios in various types of samples and the implication of the sheltering measures for cows are discussed.

Accidents↗
PubMed1990

Synthesis and 11C-labelling of the ACTH fragment analogue H-Met(O2)-Glu-His-Phe-D-Lys-Phe-OH (Org 2766) via its homocystine-containing precursor.

The hexapeptide dimer (H-Hcy-Glu-His-Phe-D-Lys-Phe-OH)2 was synthesized using solution methods and characterized. Its conversion into H-Met(O2)-Glu-His-Phe-D-Lys-Phe-OH, Org 2766, was studied on a small scale in as short a time as possible; reduction of the disulfide bond using Na/NH3, reaction with CH3I, oxidation with H2O2 and catalyst and purification by HPLC were carried out starting with 2 mg of the dimer in a total preparation time of approximately 22 min, starting with the addition of CH3I. The preparation of the 11C-labelled analogue was carried out by methylation with 11CH3I. Restrictions imposed by working with carbon-11 will be discussed.

Adrenocorticotropic Hormone↗