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Biomedical subjects

A Dozier

Publications and source records attributed to A Dozier.

7 recordsLinked to original sources
PubMed2005

Characterization of ultrafine coal fly ash particles by energy-filtered TEM.

In this study, energy-filtered transmission electron microscopy is demonstrated to be a valuable tool for characterizing ultrafine coal fly ash particles, especially those particles encapsulated in or associated with carbon. By examining a series of elemental maps (K-edge maps of C and O, and L-edge maps of Si, Al, Ti and Fe) recorded using the three-window method, considerable numbers of titanium and iron species with sizes from several nanometres to submicrometre were shown to be present, typically as oxides dispersed in the carbonaceous matrix. Crystalline phases, such as rutile and iron-rich oxide spinel, were also identified from electron diffraction patterns and high-resolution TEM images. Information about these ultrafine coal fly ash particles regarding their size, morphology, elemental composition and distribution, and crystalline phases, which has not been available previously in conventional ash studies, should be useful in toxicological studies and related environmental fields.

Air Pollutants↗
PubMed2001

Adult human olfactory stem cells.

The location of stem cells within the adult CNS makes them impractical for surgical removal and autologous transplantation. Their limited availability and histocompatibility issues further restrict their use. In contrast, olfactory neuroepithelium (ONe) located in the nasal passageways has a continuous regenerative capability and can be biopsied readily. To investigate the potential of human ONe to provide viable populations of pluripotent cells, ONe was harvested from cadavers 6-18 h postmortem, dissociated, plated and fed every 3-4 days. Heterogeneous populations of neurons, glia, and epithelia were identified with lineage-specific markers. After several weeks, 5-10% of the cultures produced a population of rapidly dividing cells, which in turn, produced neurospheres containing at least two subpopulations based on neuronal and glial specific antigens. Most contained one or more neuronal markers; a few were positive for A2B5 and/or GFAP. To determine if growth modulators would affect the neurosphere forming cells, they were exposed to dibutyryl-cAMP. The nucleotide reduced cell division and increased process formation. Although the cells had been passaged more than 70 times, their viability remained constant as shown by the MTT viability index. Donor age or sex were not limiting factors, because neurospheres have been established from cadavers of both sexes from 50 to 95 years old at time of death. The ex vivo expansion of these cells will provide a patient-specific population of cells for immunological, genetic and pharmacological evaluation. Our long-term goal is to determine the utility of these cells to facilitate CNS repair.

Aged↗
PubMed2000

Altered bone marrow cell sensitivity in the lupus-prone NZB/W mouse: regulation of CFU-GM colony formation by estrogen, tamoxifen and thrombopoietin.

Estrogen is thought to contribute to the onset of systemic lupus erythematosus (SLE) in women through mechanisms that are not completely understood. Although estrogen serves as a negative regulator in normal hematopoietic development, little research has been conducted examining alteration in hematopoietic development triggered by estrogen in lupus-susceptible individuals. We examined whether estrogen and other factors could influence colony formation of bone marrow cells obtained from normal and lupus-susceptible mice. Bone marrow cells isolated from New Zealand Black (NZB) and lupus-prone New Zealand Black and New Zealand White cross (NZB/W) mice were cultured in the presence of granulocyte-macrophage colony stimulating factor (GM-CSF) alone or in combination with estrogen, thrombopoietin (TPO), tamoxifen, estrogen and TPO. or estrogen and tamoxifen, and plated in methylcellulose culture medium. Plates were scored for the number of CFU-GM (colony forming unit granulocyte-macrophage) colonies after 6d in culture. For females of both mouse strains, estrogen significantly decreased (P < 0.05) the number of GM colonies. Co-treatment of NZB/W cells, but not NZB cells, with TPO or tamoxifen reversed the suppressive action of estrogen (P < 0.05). In contrast, while estrogen did suppress colony formation from cells of NZB/W males (P < 0.05), neither TPO nor tamoxifen reversed this effect. Our results indicate that the sensitivity of bone marrow cells isolated from both female and male NZB/W lupus-prone mice to hormones/growth factors is qualitatively different from cells of NZB mice, and suggest that hematopoietic alterations at the level of the bone marrow may be related to the pathogenesis of SLE.

Animals↗
PubMed1999

Quantitative image analysis of F-actin in endothelial cells.

OBJECTIVE: Filamentous actin (F-actin) plays a central role in maintaining endothelial barrier function. Thrombin and histamine, two inflammatory mediators that increase endothelial permeability, can alter F-actin production and distribution. In this study, we use a newly developed image analysis technique to show that these two inflammatory mediators differentially alter F-actin structure. METHODS: Human umbilical vein endothelial cells were grown to confluence and treated with either histamine (1 microM), thrombin (1 microM) or the agonist's vehicle. The endothelium was stained with BODIPY-phallodin, and digitized images were taken of the treated cells. The digitized images of individual human umbilical vein endothelial cells (HUVEC) were imported into a F-actin image analysis program (FAAP) and converted to layers, each one pixel thick. The program then determined the mean gray level (which corresponded to the amount of F-actin) in each layer starting from the outside of the cell (layer 1) and progressing in one pixel layer increments towards the center of the cell (layer 32). RESULTS: Both inflammatory mediators increased endothelial F-actin production, however, the distribution of the actin was different. Thrombin increased the presence of stress fibers, while also decreasing peripheral banding actin. In contrast, histamine had no effect on peripheral actin compared to control, but did increase the presence of F-actin stress fibers. CONCLUSIONS: These results establish that thrombin and histamine alter endothelial F-actin production in different locations within the cell, which can be quantified using an image analysis program.

Actins↗
PubMedDate not supplied

Enhancement of the indirect anti-platelet antibody test and its application to platelet immunology.

Comparisons in the same patients of platelet-bound anti-platelet antibody (APA) levels (direct test) with serum APA levels (indirect test) frequently do not give the same results. Indirect test results frequently are negative or marginally elevated even though platelet-bound antibody is greatly increased on direct testing. The most likely cause for these differences between the two tests is insufficient binding of serum antibody to test platelets in vitro. In an effort to enhance in vitro antibody binding, we examined four test modifications affecting platelet attachment. Rabbit anti-human platelet antisera (absorbed with their specific human donor leukocytes to remove HLA- and granulocyte-specific antibodies) were combined under various conditions with human platelets and tested in a modified antiglobulin consumption test utilizing rabbit IgG. The test conditions varied: incubation time of the serum APA-platelet mixture at 37 degrees C; age of the test platelet pool; ionic strength of the mixture (varied through incorporation of a low-ionic-strength solution (LISS); and vortex agitation for 30 seconds prior to the addition of sera. Optimal attachment in standard phosphate-buffered saline took place in 60 minutes using test platelets stored for either 3 or 30 days, and yielded mean values for rabbit immune sera of 9.9 fg of IgG per platelet. Preincubation controls yielded a mean of 0.7 to 1.5 fg per platelet. Incorporation of LISS or vortexing of test platelets did not affect the results of control, but both modifications substantially increased test values of immune sera to 15.8 and 17.3 fg of IgG per platelet, respectively. Combining LISS with vortexing did not further increase values.

Animals↗