American Chemical Society - 229th National Meeting: general oral and poster sessions.
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Animals↗
Biomedical subjects
Danny Chan
Publications and source records attributed to Danny Chan.
Geographic variation in posttreatment surveillance intensity for patients with cutaneous melanoma.
BACKGROUND: We investigated whether geographic determinants could account for variation in posttreatment melanoma surveillance intensity among plastic surgeons. METHODS: A custom-designed questionnaire was mailed to U.S. and non-U.S. members of the American Society of Plastic and Reconstructive Surgeons (ASPRS). Subjects were asked how they use 14 specific follow-up modalities during years 1 to 5 and 10 following primary treatment for patients with cutaneous melanoma. Repeated-measures analysis of variance was used to compare practice patterns by TNM stage, year postsurgery, U.S. census region, metropolitan statistical area (MSA), and managed care organization (MCO) penetration rate. RESULTS: Of the 1,142 respondents, 395 were evaluable. Those who did not perform melanoma surgery or follow-up were excluded. Correlation analysis showed that mean follow-up intensity for the modalities surveyed was highly correlated across TNM stages and years postsurgery. Within MSAs, only chest radiograph utilization varied significantly. The pattern of testing varied significantly by geographic region for seven modalities (office visit, computed tomography scan of the brain and chest/abdomen, alpha-fetoprotein level, 5S-cysteinyl dopa level, abdominal ultrasonogram, bone scan); in each of these, utilization by non-U.S. surgeons exceeded utilization in any U.S. census region. The pattern of testing varied significantly by MCO penetration rate for chest radiograph (greater utilization in the lowest MCO penetration rate areas) and 5S-cysteinyl dopa level (greater utilization in the highest MCO penetration rate areas). CONCLUSIONS: The intensity of posttreatment surveillance recommended by ASPRS members caring for patients with cutaneous melanoma varies markedly. This analysis provides the first evidence that geographic factors significantly affect the surveillance strategies of clinicians following patients with cutaneous melanoma. Variation by census region was most prominent, although the size of detected differences was small.
Censuses↗
An externally fixed femoral fracture model for mice.
Transgenic and knockout mouse models can be used to help understand the molecular mechanisms of fracture repair. This study examines the feasibility of applying an external fixator to the mouse femur as one model for studying fracture repair. The external fixator consisted of two aluminum blocks connected by two rods. Four pins are used to connect the blocks to the bone. Mechanical characterization of the fixators was carried out prior to their use. Sixty-two wild type mice with bilateral femoral fractures were created using an open technique and fixed using the fixator. The progress of fracture healing was monitored radiologically before sacrifice and by mechanical testing and histology after sacrifice. Initially four mice died intraoperatively from excessive blood loss, the intraoperative mortality was subsequently reduced by subcutaneous saline infusion. The bone healed between 14 and 21 days after fracture and remodeled by 60 days. Both radiological and mechanical assessments showed a steady progression of bone healing. Histology demonstrated callus and endochondral bone formation. This study demonstrated that it is possible to create a mouse femoral fracture model stabilized by external fixation and will provide an additional model to the understanding of fracture healing in transgenic and knockout mice.
Animals↗
MT1-MMP-dependent and -independent regulation of gelatinase A activation in long-term, ascorbate-treated fibroblast cultures: regulation by fibrillar collagen.
Human skin fibroblasts were cultured long-term in the presence of ascorbic acid to allow formation of a three-dimensional collagen matrix, and the effects of this on activation of secreted matrix metalloproteinase-2 (MMP-2) were examined. Accumulation of collagen over time correlated with increased levels of both mature MMP-2 and cell-associated membrane type 1-MMP (MT1-MMP), and subsequently increased mRNA levels for MT1-MMP, providing temporal resolution of the "nontranscriptional" and "transcriptional" effects of collagen on MT-1MMP functionality. MMP-2 activation by these cultures was blocked by inhibitors of prolyl-4-hydroxylase, or when fibroblasts derived from the collagen alpha1(I) gene-deficient Mov-13 mouse were used. MMP-2 activation by the Mov-13 fibroblasts was rescued by transfection of a full-length alpha1(I) collagen cDNA, and to our surprise, also by transfection with an alpha1(I) collagen cDNA carrying a mutation at the C-proteinase cleavage, which almost abrogated fibrillogenesis. Although studies with ascorbate-cultured MT1-MMP-/- fibroblasts showed that MT1-MMP played a significant role in the collagen-induced MMP-2 activation, a residual MT1-MMP-independent activation of MMP-2 was seen which resembled the level of MMP-2 activation persisting when wild-type fibroblasts were cultured in the presence of both ascorbic acid and MMP inhibitors. We were also unable to block this residual activation with inhibitors specific for serinyl, aspartyl, or cysteinyl enzymes.
Ascorbic Acid↗
Evaluation of patients with clinically suspected melanoma recurrence: current practice patterns of plastic surgeons.
The optimal extent-of-disease evaluation for patients with clinically suspected melanoma recurrence is not known. The available modalities are numerous and many are expensive. We documented the extent of work-up carried out by plastic surgeons when their patients with melanoma develop clinical recurrence. A custom-designed questionnaire was mailed to a random sample (n=3,032) of the 4,320 members of the American Society of Plastic and Reconstructive Surgeons (ASPRS). Subjects were asked which specific laboratory tests and imaging studies they would order for a patient with initial T2N0M0 disease treated with curative intent who later presented with either regional nodal metastases or pulmonary metastases. We measured the variability in practice patterns among surgeons and estimated the effects of physician age, U.S. census region, health maintenance organization (HMO) penetration rates, and type of recurrence (regional versus systemic) on work-up intensity. Of the 1,142 questionnaires completed (38%), 395 (35%) were evaluable. Non-evaluability was usually due to lack of melanoma patient follow-up in surgeons' practices. Lesion biopsy, chest X-ray, complete blood count, liver function tests, and computed tomography were frequently used, but there was no consensus for most modalities. More tests, particularly computed tomography, were utilized for evaluating systemic recurrence than for regional recurrence (p<0.05). The intensity of work-up differed significantly (p<0.05) by surgeon age for three diagnostic tests but not by U.S. census region or HMO penetration rate. This is the first empirical data on this subject from a large sample of an international society of highly credentialed experts. The lack of consensus for most tests in current practice is presumably due to multiple factors, including the lack of evidence supporting any particular strategy.
Adult↗
Structural investigations of human hairs by spectrally resolved ellipsometry.
Human hair is a biological layered system composed of two major layers, the cortex and the cuticle. We show spectrally resolved ellipsometry measurements of the ellipsometric parameters Psi and Delta of single human hairs. The spectra reflect the layered nature of hair and the optical anisotropy of the hair's structure. In addition, measurements on strands of human hair show a high reproducibility of the ellipsometric parameters for different hair fiber bundles from the same person. Based on the measurements, we describe a dielectric model of hair that explains the spectra in terms of the dielectric properties of the major parts of hair and their associated layer thicknesses. In addition, surface roughness effects modeled by a roughness layer with a complex refractive index given by an effective medium approach can be seen to have a significant effect on the measurements. We derive values for the parameters of the cuticle surface roughness layer of the thickness d(ACu)=273 to 360 nm and the air inclusion fA=0.6 to 5.7%.
Algorithms↗
Single laboratory validation of a method for the determination of hydroxymethylfurfural in honey by using solid-phase extraction cleanup and liquid chromatography.
A method is described for the determination of hydroxymethylfurfural (HMF) in honey. The method, which is based on solid-phase extraction cleanup followed by liquid chromatography (LC) with UV absorbance detection, was tested on a variety of different honey types: liquid, set, blended, filtered, crystalline, and comb honey. A sample of honey fortified with a known amount of HMF acted as an in-house reference material. LC with diode-array detection showed that the HMF peak did not contain any peaks of coeluting interfering species. Stability studies showed that honey samples should not be repeatedly frozen and thawed because the temperature changes caused a gradual increase in the HMF concentration. It was also shown that aqueous HMF standard solutions should be kept in the dark at 4 degrees C to avoid degradation of the HMF. The method was internally validated, and the measurement uncertainty was estimated to be +/-9.0 at 40 mg/kg, the legal limit. A comparison of the relative standard uncertainty with the Horwitz relative standard deviation showed that the method was suitable for its purpose and should be validated by a collaborative trial.
Chemistry Techniques, Analytical↗
Determination of deoxynivalenol in cereals and cereal products by immunoaffinity column cleanup with liquid chromatography: interlaboratory study.
An interlaboratory study was performed on behalf of the UK Food Standards Agency to evaluate the effectiveness of an immunoaffinity column cleanup liquid chromatographic (LC) method for the determination of deoxynivalenol in a variety of cereals and cereal products at proposed European regulatory limits. The test portion was extracted with water. The sample extract was filtered a applied to an immunoaffinity column. After being washed with water, the deoxynivalenol was eluted with acetonitrile or methanol. Deoxynivalenol was quantitated by reversed-phase LC with UV determination. Samples of artificially contaminated wheat-flour, rice flour, oat flour, polenta, and wheat based breakfast cereal, naturally contaminated wheat flour, and blank (very low level) samples of each matrix were sent to 13 collaborators in 7 European countries. Participants were asked to spike test portions of all samples at a range of deoxynivalenol concentrations equivalent to 200-2000 ng/g deoxynivalenol. Average recoveries ranged from 78 to 87%. Based on results for 6 artificially contaminated samples (blind duplicates), the relative standard deviation for repeatability (RSDr) ranged from 3.1 to 14.1%, and the relative standard deviation for reproducibility (RSDR) ranged from 11.5 to 26.3%. The method showed acceptable within-laboratory and between-laboratory precision for all 5 matrixes, as evidenced by HorRat values < 1.3.
Acetonitriles↗
Feasibility study for the production of certified calibrants for the determination of deoxynivalenol and other B-trichothecenes: intercomparison study.
Thirteen European laboratories experienced in the analysis of mycotoxins participated in an intercomparison study within a European Commission-funded project. Goals of the study were to check the fitness for purpose of a small batch of gravimetrically prepared calibrants; to compare individually prepared calibrants with common calibrants; to check the feasibility of toxin mixtures as calibrant solutions; and to give recommendations on the production of future certified reference materials (CRMs) with regard to the nature of the calibrant and the means of certification. Each laboratory received ampules of each common calibrant containing single toxins [solution containing either deoxynivalenol (DON), 3-acetyl-DON (3-Ac-DON), nivalenol (NIV), or 15-acetyl-DON (15-Ac-DON)] and 3 ampules of toxin-mixture (solutions of DON + 3-Ac-DON + NIV in acetonitrile) of known concentrations (about 20 microg/mL). Ampules with single toxins (solution containing either DON, 3-Ac-DON, NIV, or 15-Ac-DON) and a toxin-mixture (solutions of DON + 3-Ac-DON + NIV in acetonitrile) of unknown concentrations were distributed to the participants for quantification. The participating laboratories used mainly high-performance liquid chromatography (HPLC)-diode array detection UV for DON, 3-Ac-DON, NIV, and 15-Ac-DON; gas chromatography-electron capture detection (GC-ECD) and GC-mass spectrometry methods were used sparingly. Linear calibration curves were achieved by >90% of the participants. Relative between-day variation (RSDr) of 26% of the laboratories was greater than the target value of 5% for HPLC, and RSDr of 32% of the laboratories was greater than the desired value of 10% for GC. Relative between-laboratory variation (RSDR) of the GC results obtained with single common calibrants was greater than the target value of 16% for all laboratories. RSDR of the HPLC results for the common unknown single toxin solutions was less than the target value of 8% except for 15-Ac-DON. Generally, better recoveries were observed from common calibrants (102% for mix calibrants and 98% for single calibrants) than from individually prepared calibrants (95%). This international comparison study clearly showed the high scattering of results in the analysis of type-B trichothecenes, particularly when GC was used. Obviously, this intercomparison study was not suited for the certification of B-trichothecenes. A certification of the proposed calibrant material was therefore recommended on the basis of its gravimetrical preparation.
Calibration↗