Biomedical subjects
Publications and source records attributed to C Benz.
The purpose of this investigation was to evaluate the precision of optical impressio obtained with the Cerec-device. Cerec provides a linear correlation between z-data and altitude (r = 1), one bit representing 49 microns. Repeated measurements deliver pixel-z-data within a range of +/- 49 microns and surfaceaverages (484 pixel) within +/- 5 microns. Deviations occur near areas with parallel orientation to the direction of measurement.
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The latest version of the Radiovisiography-system was evaluated in comparison to its predecessor and a high speed periapical film (Agfa Dentus M4). Both RVG-systems proved to have the same sensitivity and are capable of displaying a similar contrast range. Nevertheless additional functions of the new system allow a much better visualisation of the radiographed structure. Compared with Dentus M4 periapical films the RVG-System provides less sensitivity but a wider range of contrast.
Unlike manual and electric toothbrushes, the brush head of the Interplak instruments remains stationary while ten tufts of bristle rotate. The efficacy of this new system was evaluated in comparison to a conventional electric toothbrush (Braun dental d3). When used for the first time the Interplak instrument proved to be more effective in reducing plaque. After training periods of 2 and 4 weeks there was, however, no significant difference between products.
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A comparison of physical properties has been made between conventional intraoral films and images made with the RadioVisioGraphy (RVG) system, a unit based on the charged coupled device. The RVG system uses considerably reduced levels of radiation to produce an image immediately after exposure. RVG resolution is slightly lower than that with silver halide emulsion films; however, radiographic information may be increased by electronic image treatment.
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Two new periapical films (Agfa Dentus M 4, Dupont Super Dozahn HS) were evaluated in comparison to Kodak-Ultraspeed and -Ektaspeed films. Dentus M 4 proved to be the fastest film available. Though higher sensitivity results in less contrast, faster films can in most cases be used with the advantage of maximal dose reduction.
RadioVisioGraphie, an electronic system that allows taking intraoral radiographs without film and developing time, was evaluated in comparison to conventional dental films (Ultraspeed D, Kodak). The RVG-system proved to be much more sensitive and capable of displaying a wider object range than film.
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During high speed cavity preparation the vibration burden of human teeth was evaluated in comparison between turbine- and micromotor-driven handpieces. The acceleration spectra of different burs showed an advantage of the air-driven handpiece.
The effects of estradiol (E2) on c-myc proto-oncogene expression were studied in the estrogen receptor (ER)-positive human breast cancer cell line, MCF-7. A biphasic modulation in c-myc mRNA levels occurs during the first 24 h of E2 (1 nM) exposure and in the absence of changes in MCF-7 culture growth, with transcript levels rising 4-6-fold within 1 h, returning to near base-line level after 3-6 h, and increasing again after 24 h of exposure. In contrast, the growth-inhibiting antiestrogen, tamoxifen (1 microM), reduces c-myc to 20% of the pretreatment level within 3-6 h of exposure, and this early decline is followed by a gradual return toward base-line level after continuous 72-h treatment. In ER-negative cells there is no change in c-myc expression following E2 exposure. MCF-7 nuclear runon assays show that c-myc transcription rates remain unchanged from base line for 24 h after E2 administration; as well, cycloheximide inhibition of protein synthesis superinduces c-myc expression and prevents E2 modulation of transcript levels. These results indicate that post-transcriptional modulation of c-myc by E2 is mediated by a labile degradative protein or otherwise dependent on active protein synthesis. We also developed MCF/nm and MCF/dm sublines by transfecting normal cells with human c-myc exons 2-3, transcriptionally driven by a retroviral long terminal repeat. Expression of the transfected c-myc genes in these sublines remains constant and elevated 10-fold, while transcript levels from the endogenous proto-oncogene continue to be modulated by E2. These findings suggest that in ER-positive breast cancer cells, E2 can modulate c-myc mRNA levels by a post-transcriptional mechanism that depends on gene sequences upstream from c-myc exon 2.
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The antitumor toxicity of gossypol was measured in 6 human carcinoma cell lines and compared with its toxicity against human bone marrow stem cells. Marrow cells were more resistant than any of the tumor cell lines, and tumor cell sensitivity depended on the content of intracellular LDH-M. [31P]-Magnetic resonance spectroscopy showed decline in tumor ATP levels occurring within 24 hours of treatment, suggesting that this non-invasive technique may serve as an early biochemical monitor of gossypol toxicity.
Specific genetic alterations are observed in human breast cancer, but little is known about when these occur in the evolution of the disease. Three breast cancer effusions that occurred sequentially in a single patient were examined. Common cytogenic abnormalities were found in all effusion samples suggesting a single progenitor metastatic cell. Only the last effusion, however, exhibited a mutation of the c-K-ras gene and a loss of heterozygosity at the c-H-ras locus. These specific genetic abnormalities detected in the last effusion was correlated with improved in vitro growth of the primary cells, and with the ability to establish breast cancer cell lines. Thus a mutant ras gene and the loss of heterozygosity at the c-H-ras locus were associated with a more aggressive tumor phenotype occurring late in the course of this patient's disease and not with the initiation of the primary breast cancer, or in the establishment of metastases.
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