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Biomedical subjects

D R Christensen

Publications and source records attributed to D R Christensen.

8 recordsLinked to original sources
PubMed1997

Sclerosing epithelioid fibrosarcoma: short T2 on MR imaging.

A case of sclerosing epithelioid fibrosarcoma and its appearance on MRI is presented. The tumor showed a zonal architecture on MRI with a large central core of very low signal intensity and a peripheral rim of intermediate to high signal intensity on T1- and T2-weighted spin echo pulse sequences. The core showed decreased cellularity with dense collagen deposition on histologic examination, and the peripheral zone increased cellularity with increased nuclear atypia. The presence of a prominent region of very low signal intensity on T1- and T2- weighted images can be seen with neural tumors, giant cell tumor of the tendon sheath, aggressive fibromatosis, and, in rare instances, with soft tissue sarcomas rich in collagen.

Adult↗
PubMed1997

Correlation of PCR-detected clonal gene rearrangements with bone marrow morphology in patients with B-lineage lymphomas.

Bone marrow biopsy is the conventional staging and posttherapy evaluation method for assessing marrow involvement by lymphoma. Polymerase chain reactions (PCR) for antigen receptor rearrangements have the potential to increase the detection of minimal degrees of marrow involvement. The present study is a concurrent morphologic and PCR evaluation of 225 staging or posttherapy marrow biopsies from 127 patients with B-lineage non-Hodgkin's lymphoma. The biopsies were morphologically categorized into four groups: group 1 (positive for lymphoma), 60 biopsies (27%); group 2 (suspicious for lymphoma), 20 biopsies (9%); group 3 (lymphocytic lesions of indeterminate biology), 22 biopsies (10%); and group 4 (negative for lymphoma), 123 biopsies (54%). Molecular studies were performed on concurrently obtained aspirates and used consensus immunoglobulin-heavy-chain (IgH) and IgH/bcl-2 gene PCR primers. A molecular clone was detected in 53 of the 225 aspirates (24%): group 1, 34 aspirates (57%); group 2, five aspirates (25%); group 3, one aspirate (5%); and group 4, 13 aspirates (11%). A PCR-positive aspirate was present in 47% of follicular lymphomas, 58% of diffuse large cell lymphomas, and 72% of the other lymphomas in the group I specimens. Morphology or PCR was positive in 79 of the 225 cases (35%). The molecular detection of clonality in the aspirate DNA from cases with positive morphologic findings was lower than anticipated. The discordance between morphology and PCR results may be related to sample variation between the trephine biopsy and aspirate, a failure to aspirate sufficient lymphoma cells, or insufficient primer homology for amplification. DNA extracted from trephine sections may provide results more concordant with morphology, because PCR detected a clone in 10 of 11 DNA specimens extracted from trephine biopsies with positive morphologic findings and PCR negative aspirates.

Base Sequence↗
PubMed1994

Characterization of exposure and dose of man made vitreous fiber in experimental studies.

The use of fibrous test materials in in vivo experiments introduces a number of significant problems not associated with nonfibrous particulates. The key to all aspects of the experiment is the accurate characterization of the test material in terms of fiber length, diameter, particulate content, and chemistry. All data related to fiber properties must be collected in a statistically sound manner to eliminate potential bias. Procedures similar to those outlined by the National Institute of Occupational Safety and Health (NIOSH) or the World Health Organization (WHO) must be the basis of any fiber characterization. The test material to which the animal is exposed must be processed to maximize the amount of respirable fiber and to minimize particulate content. The complex relationship among the characteristics of the test material, the properties of the delivery system, and the actual dose that reaches the target tissue in the lung makes verification of dose essential. In the case of man-made vitreous fibers (MMVF), dose verification through recovery of fiber from exposed animals is a complex task. The potential for high fiber solubility makes many of the conventional techniques for tissue preservation and digestion inappropriate. Processes based on the minimum use of aggressive chemicals, such as cold storage and low temperature ashing, are potentially useful for a wide range of inorganic fibers. Any processes used to assess fiber exposure and dose must be carefully validated to establish that the chemical and physical characteristics of the fibers have not been changed and that the dose to the target tissue is completely and accurately described.

Animals↗