Biomedical subjects

Ann Roberts

Publications and source records attributed to Ann Roberts.

8 recordsLinked to original sources

PubMed2006

Simultaneous multidopant investigation of rare-earth-doped optical fibers by an ion microprobe.

The relative distribution of five elements present in the core area of several optical fiber samples has been obtained by utilizing nanoscale-secondary ion mass spectrometry. A strong correlation between the rare-earth (RE) ion and aluminum was observed, consistent with aluminum's improving the solubility of the RE ion. The central dip in distribution was less severe than that observed for germanium, characteristic of the collapse process during fabrication of the fiber preform.

Journal Article↗

PubMed2006

Single cell volume measurement by quantitative phase microscopy (QPM): a case study of erythrocyte morphology.

The measurement of the volume of intact, viable cells presents challenging problems in many areas of experimental and diagnostic science involved in the evaluation of cellular morphology, growth and function. This investigation details the implementation of a recently developed quantitative phase microscopy (QPM) method to measure the volume of erythrocytes under a range of osmotic conditions. QPM is a computational approach which utilizes simple bright field optics to generate cell phase maps which, together with knowledge of the cellular refractive index, may be used to measure cellular volume. Rat erythrocytes incubated in imidazole-buffered solutions (22 degrees C) of graded tonicity were analysed using QPM (n=10 cells/group, x63, 0.8 NA objective). Erythrocyte refractive index (1.367) was measured using a combination of phase and morphological data obtained from cells adopting spherical geometry under hypotonic conditions. Phase-computed volume increased with decreasing solution osmolality: 42.8 +/- 2.4, 48.7 +/- 2.3, 62.6 +/- 2.3, 90.8 +/- 7.7 microm3 in solutions of 540, 400, 240, and 170 mosmol/kg respectively. These volume changes were associated with crenated, bi-concave and spherical morphological states associated with increasing tonicity. This investigation demonstrates that QPM is a valid, simple and non-destructive approach for measuring cellular phase properties and volume. QPM cell volume analysis represents a significant advance in viable cell experimental capability and provides for acquisition of 'real-time' data - an option not previously available using other approaches.

Animals↗

PubMed2005

Refractive index measurement in viable cells using quantitative phase-amplitude microscopy and confocal microscopy.

BACKGROUND: The refractive index (RI) of cellular material provides fundamental biophysical information about the composition and organizational structure of cells. Efforts to describe the refractive properties of cells have been significantly impeded by the experimental difficulties encountered in measuring viable cell RI. In this report we describe a procedure for the application of quantitative phase microscopy in conjunction with confocal microscopy to measure the RI of a cultured muscle cell specimen. METHODS: The experimental strategy involved calculation of cell thickness by using confocal optical sectioning procedures, construction of a phase map of the same cell using quantitative phase microscopy, and selection of cellular regions of interest to solve for the cell RI. RESULTS: Mean cell thickness and phase values for six cell regions (five cytoplasmic and one nuclear) were determined. The average refractive index calculated for cytoplasmic and nuclear regions was 1.360 +/- 0.004. The uncertainty in the final RI value represents the technique measurement error. CONCLUSIONS: The methodology we describe for viable cell RI measurement with this prototype cell has broad generic application in the study of cell growth and functional responses. The RI value we report may be used in optical analyses of cultured cell structure and morphology.

Cell Survival↗

PubMed2005

X-ray imaging: a generalized approach using phase-space tomography.

We discuss the role of coherence in x-ray imaging and consider how phase-space tomography can be used to extract information about partial coherence. We describe the application of phase-space tomography to x-ray imaging and recover the spatial coherence properties of a one-dimensional soft (1.5 keV) x-ray beam from a synchrotron undulator source. We present phase-space information from a Young's experiment and observe negative regions in the quasi-probability distribution. We show that, given knowledge of the coherence of the beam, we can use partially coherent diffraction data to recover fully coherent information, and we present some simple experimental demonstrations of this capability.

Algorithms↗

PubMed2004

A gene-driven ENU-based approach to generating an allelic series in any gene.

N-ethyl-N-nitrosourea (ENU) introduces mutations throughout the mouse genome at relatively high efficiency. Successful high-throughput phenotype screens have been reported and alternative screens using sequence-based approaches have been proposed. For the purpose of generating an allelic series in selected genes by a sequence-based approach, we have constructed an archive of over 4000 DNA samples from individual F1 ENU-mutagenized mice paralleled by frozen sperm samples. Together with our previously reported archive, the total size now exceeds 6000 individuals. A gene-based screen of 27.4 Mbp of DNA, carried out using denaturing high-performance liquid chromatography (DHPLC), found a mutation rate of 1 in 1.01 Mbp of which 1 in 1.82 Mbp were potentially functional. Screening of whole or selected regions of genes on subsets of the archive has allowed us to identify 15 new alleles from 9 genes out of 15 tested. This is a powerful adjunct to conventional mutagenesis strategies and has the advantage of generating a variety of alleles with potentially different phenotypic outcomes that facilitate the investigation of gene function. It is now available to academic collaborators as a community resource.

Alkylating Agents↗

PubMed2004

Quantitative phase microscopy: a new tool for investigating the structure and function of unstained live cells.

1. The optical transparency of unstained live cell specimens limits the extent to which information can be recovered from bright-field microscopic images because these specimens generally lack visible amplitude-modulating components. However, visualization of the phase modulation that occurs when light traverses these specimens can provide additional information. 2. Optical phase microscopy and derivatives of this technique, such as differential interference contrast (DIC) and Hoffman modulation contrast (HMC), have been used widely in the study of cellular materials. With these techniques, enhanced contrast is achieved, which is useful in viewing specimens, but does not allow quantitative information to be extracted from the phase content available in the images. 3. An innovative computational approach to phase microscopy, which provides mathematically derived information about specimen phase-modulating characteristics, has been described recently. Known as quantitative phase microscopy (QPM), this method derives quantitative phase measurements from images captured using a bright-field microscope without phase- or interference-contrast optics. 4. The phase map generated from the bright-field images by the QPM method can be used to emulate other contrast image modes (including DIC and HMC) for qualitative viewing. Quantitative phase microscopy achieves improved discrimination of cellular detail, which permits more rigorous image analysis procedures to be undertaken compared with conventional optical methods. 5. The phase map contains information about cell thickness and refractive index and can allow quantification of cellular morphology under experimental conditions. As an example, the proliferative properties of smooth muscle cells have been evaluated using QPM to track growth and confluency of cell cultures. Quantitative phase microscopy has also been used to investigate erythrocyte cell volume and morphology in different osmotic environments. 6. Quantitative phase microscopy is a valuable, new, non-destructive, non-interventional experimental tool for structural and functional cellular investigations.

Animals↗

PubMed2003

Nondestructive imaging of a type I optical fiber Bragg grating.

Nondestructive images of refractive-index variation within a type I fiber Bragg grating have been recorded by the differential interference contrast imaging technique. The images reveal detailed structure within the fiber core that is consistent with the formation of Talbot planes in the diffraction pattern behind the phase mask that had been used to fabricate the grating.

Journal Article↗

PubMed2002

Promotion of social change: a conceptual framework.

This paper argues for the need to advance promotion efforts and proposes a conceptual framework for promotion of social change. A brief review is presented of traditional frameworks for the prevention of mental and social disorders and the promotion of wellness and social competencies, with attention to the ways in which promotion of social change extends and departs from these frameworks. In a framework for promoting social change, we advocate for promoting dynamic processes within systems, rather than outcomes within individuals. Systems are viewed as flexible and capable of facilitating multiple adaptive pathways for individuals and groups. Promoting social change also involves careful attention to critical analysis, values, language, and contextual processes. Examples are discussed throughout to illustrate how these principles have been used in the past and can be implemented in future efforts to promote social change.

Health Planning↗