Biomedical subjects

Rebecca Williams

Publications and source records attributed to Rebecca Williams.

9 recordsLinked to original sources

PubMed2007

Closed-loop, multiobjective optimization of two-dimensional gas chromatography/mass spectrometry for serum metabolomics.

Metabolomics seeks to measure potentially all the metabolites in a biological sample, and consequently, we need to develop and optimize methods to increase significantly the number of metabolites we can detect. We extended the closed-loop (iterative, automated) optimization system that we had previously developed for one-dimensional GC-TOF-MS (O'Hagan, S.; Dunn, W. B.; Brown, M.; Knowles, J. D.; Kell, D. B. Anal. Chem. 2005, 77, 290-303) to comprehensive two-dimensional (GCxGC) chromatography. The heuristic approach used was a multiobjective version of the efficient global optimization algorithm. In just 300 automated runs, we improved the number of metabolites observable relative to those in 1D GC by some 3-fold. The optimized conditions allowed for the detection of over 4000 raw peaks, of which some 1800 were considered to be real metabolite peaks and not impurities or peaks with a signal/noise ratio of less than 5. A variety of computational methods served to explain the basis for the improvement. This closed-loop optimization strategy is a generic and powerful approach for the optimization of any analytical instrumentation.

Biomarkers↗

PubMed2006

Proteasome inhibition to maximize the apoptotic potential of cytokine therapy for murine neuroblastoma tumors.

Human neuroblastomas possess several mechanisms of self-defense that may confer an ability to resist apoptosis and contribute to the observed difficulty in treating these tumors in the clinical setting. These molecular alterations may include defects in proapoptotic genes as well as the overexpression of prosurvival factors, such as Akt among others. As a key regulator of the turnover of proteins that modulate the cell cycle and mechanisms of apoptosis, the proteasome could serve as an important target for the treatment of neuroblastoma. The present studies provide the first evidence that bortezomib, a newly approved inhibitor of proteasome function, inhibits phosphorylation of Akt, induces the translocation of proapoptotic Bid, and potently enhances the apoptosis of murine neuroblastoma tumor cells in vitro. Furthermore, in that inhibitors of the Akt pathway can sensitize otherwise resistant TBJ/Neuro-2a cells to apoptosis induced by IFN-gamma plus TNF-alpha, we hypothesized that bortezomib also could sensitize these cells to IFN-gamma plus TNF-alpha. We demonstrate for the first time that bortezomib not only up-regulates the expression of receptors for IFN-gamma and TNF-alpha on both TBJ neuroblastoma and EOMA endothelial cell lines, but also markedly enhances the sensitivity of these cells to apoptosis induced by IFN-gamma plus TNF-alpha in vitro. Furthermore, bortezomib enhances the in vivo antitumor efficacy of IFN-gamma/TNF-alpha-inducing cytokines, including both IL-2 and IL-12 in mice bearing well-established primary and/or metastatic TBJ neuroblastoma tumors. Collectively, these studies suggest that bortezomib could be used therapeutically to enhance the proapoptotic and overall antitumor activity of systemic cytokine therapy in children with advanced neuroblastoma.

Animals↗

PubMed2006

In vivo delivery of fluoresceinated dextrans to the murine growth plate: imaging of three vascular routes by multiphoton microscopy.

Bone elongation by endochondral ossification occurs through the differentiation cascade of chondrocytes of cartilaginous growth plates. Molecules from the systemic vasculature reach the growth plate from three different directions: epiphyseal, metaphyseal, and a ring vessel and plexus associated with the perichondrium. This study is an analysis of the real-time dynamics of entrance of fluoresceinated tracers of different molecular weights into the growth plate from the systemic vasculature and tests the hypothesis that molecular weight is a key variable in the determination of both the directionality and the extent of tracer movement into the growth plate. Multiphoton microscopy was used for direct in vivo imaging of the murine proximal tibial growth plate in anesthetized 4- to 5-week-old transgenic mice with green fluorescent protein linked to the collagen II promoter. Mice were given an intracardiac injection of either fluorescein (332.3 Da) or fluoresceinated dextrans of 3, 10, 40, 70 kDa, singly or sequentially. For each tracer, directionality and rate of arrival, together with extent of movement within the growth plate, were imaged in real time. For small molecules (up to 10 kDa), vascular access from all three directions was observed and entrance was equally permissive from the metaphyseal and the epiphyseal sides. Within our detection limit (a few percent of vascular concentration), 40 kDa and larger dextrans did not enter. These results have implications both for understanding systemic and paracrine regulation of growth plate chondrocytic differentiation, as well as variables associated with effective drug delivery to growth plate chondrocytes.

Animals↗

PubMed2006

The detection of phenotypic differences in the metabolic plasma profile of three strains of Zucker rats at 20 weeks of age using ultra-performance liquid chromatography/orthogonal acceleration time-of-flight mass spectrometry.

Analysis of biological fluids using ultra-performance liquid chromatography/mass spectrometry (UPLC/MS) (metabonomics) can allow new insights to be gained into disease processes, with advances in chromatographic techniques enabling the detection of thousands of metabolites. In this work metabonomics has been used to investigate the metabolic processes involved in type II diabetes in the Zucker obese rat. Plasma was analyzed from three different strains, the Zucker (fa/fa) obese, Zucker lean and the lean/(fa) obese cross. Using UPLC/MS, ca. 10,000 ions were detected due to the narrow peak widths and excellent peak shapes achieved with this technology. Confidence in the chromatographic performance was demonstrated by the use of quality control standards. The positive and negative ion total ion chromatograms obtained from the three strains were readily distinguishable using multivariate statistical analysis. The greatest difference was observed between the Zucker lean and Zucker lean/(fa) rats compared to the Zucker (fa/fa) obese rats. Positive ions m/z 220 (4.36 min), 282(3.78 min), 359 (5.33 min) and 405 (7.77 min) were elevated in the plasma derived from Zucker lean rats whilst ions m/z 385 (6.80 min) and 646 (4.36 min) were at a lower concentration compared to the plasma from the Zucker (fa/fa) obese animals. Negative ions elevated in the Zucker lean rats included m/z 212 (2.30 min), 514 (2.85 min), 295 (4.39 min), 329 (3.11 min), 343 (2.86 min) and 512 (2.86 min) with ions m/z 538 (4.18 min), 568 (4.18 min), 568 (5.09 min) and 612 (4.30 min) being raised in the samples derived from Zucker (fa/fa) obese animals. The ion m/z 514 (3.85 min) was found to correspond to taurocholate, providing further support for an involvement of taurine metabolism in diabetes.

Animals↗

PubMed2006

A metabonomic analysis of plasma from Zucker rat strains using gas chromatography/mass spectrometry and pattern recognition.

Plasma obtained from three strains of Zucker rats was analysed using capillary gas chromatography/mass spectrometry (GC/MS) to obtain global metabolite profiles as part of a series of metabonomic investigations of animal models of diabetes. Samples were obtained from 20-week-old male wild-type Zucker lean, (fa/fa) obese and lean/(fa) animals and were analysed following protein precipitation, using acetonitrile, and derivatisation. Subsequent data analysis using principal components analysis (PCA) and orthogonal projection to latent structures (OPLS) revealed differences between the plasma metabolite profiles of the three strains, with those of the Zucker lean and the lean/(fa) crosses being similar to each other whilst differing from the (fa/fa) obese strain.

Animals↗

PubMed2005

HPLC-MS-based methods for the study of metabonomics.

The development and use of HPLC-MS for the study of metabonomics is reviewed. To date the technique has been applied to the analysis of urine samples obtained from studies in rodents in investigations of physiological variation (e.g., factors such as strain, gender, diurnal variation, etc.) and toxicity. Examples are provided of the use of conventional HPLC, capillary methods and the recently introduced high-resolution systems based on a combination of high pressure and small particle size ("UPLC"). Comparison is also made of the use of 1H NMR spectroscopy and HPLC-MS for the analysis of biofluid samples and the advantages and limitations of the two approaches are assessed. Likely future developments are considered.

Animals↗

PubMed2005

Axenfeld-Rieger malformation and distinctive facial features: Clues to a recognizable 6p25 microdeletion syndrome.

Deletion of distal 6p is associated with a distinctive clinical phenotype including Axenfeld-Rieger malformation, hearing loss, congenital heart disease, dental anomalies, developmental delay, and a characteristic facial appearance. We report the case of a child where recognition of the specific ocular and facial phenotype, led to identification of a 6p microdeletion arising from a de novo 6:18 translocation. Detailed analysis confirmed deletion of the FOXC1 forkhead gene cluster at 6p25. CNS anomalies included hydrocephalus and hypoplasia of the cerebellum, brainstem, and corpus callosum with mild to moderate developmental delay. Unlike previous reports, hearing was normal.

Abnormalities, Multiple↗

PubMed2004

Formic acid excretion in rats and mice exposed to bromodichloromethane: a possible link to renal tubule cell proliferation in long-term studies.

Male F344 rats exposed to bromodichloromethane (BDCM) by gavage at 50 or 100 mg/kg/day for 5 days a week for 28 days excreted large amounts of formic acid in their urine, which was accompanied by a change in urinary pH. Male B6C3F1 mice exposed to BDCM at 25 or 50 mg/kg/day for 5 days a week for 28 days also excreted increased amounts of formic acid in their urine. In rats, formate excretion was dose and time dependant, being markedly elevated after four doses and remaining at that level after 3 weeks of dosing at 100 mg/kg/day BDCM, while at 50 mg/kg/day there was some suggestion of a decline after 3 weeks. In contrast, in mice formate excretion did not start to a major extent until 3 weeks of dosing, with the biggest response at 4 weeks. There was no increase in clinical chemistry markers of liver or kidney injury in either rats or mice following 28-day exposure to BDCM. However, morphological examination of the kidneys showed some mild renal tubule injury in two out of five rats exposed to 100 mg/kg/day BDCM. This was associated with a marked increase in cell proliferation in the renal cortex of all rats exposed to 100 mg/kg/day. No increase in cell proliferation was seen in the renal cortex of rats exposed to BDCM at 50 mg/kg/day, or in mice exposed to 25 or 50 mg/kg/day BDCM for 28 days. Long-term exposure to formic acid is known to cause kidney damage, suggesting that excretion of this acid may be a contributory factor to the increase in cell proliferation and kidney damage seen in the longer-term studies with BDCM.

Administration, Oral↗

PubMed2004

Acquired brain injury, visual attention, and the useful field of view test: A pilot study.

OBJECTIVE: To compare the findings of the Useful Field of View (UFOV) test with those of conventional neuropsychologic tests to determine the utility of the UFOV test as a measure of attention in a population with brain injury. DESIGN: Cohort study. SETTING: Freestanding rehabilitation hospital. PARTICIPANTS: Fifteen inpatients with severe brain injury. INTERVENTIONS: Not applicable. MAIN OUTCOME MEASURES: UFOV test, FIM\T instrument, length of stay (LOS), and standard neuropsychologic testing. RESULTS: The UFOV subtest UF2 correlated strongly with the other 2 subtests, UF1 and UF3. The UF2 subtest correlated most strongly with paper and pencil tests of visual attention. The UF2 predicted 52% of the FIM change and 60% of the LOS variance, second only to admission FIM score, which predicted 75% and 80% of FIM change and LOS variance, respectively. CONCLUSIONS: Among the patients in our study, the UFOV test can be used to determine the visual divided attention of patients with acquired brain injury. The results also showed that the UFOV test correlated with LOS and FIM change in patients with acquired brain injury recovering in a rehabilitation facility. Because the UFOV test is much more quickly administered and scored than other measures of attention and divided attention, these results suggest that the UFOV test may provide an easy means to measure a critical variable in the population with head injury.

Adult↗