PubMed Health⌕ Search

Biomedical subjects

Michael H Fox

Publications and source records attributed to Michael H Fox.

16 recordsLinked to original sources
PubMed2006

Comparison of the mutagenic potential of 17 physical and chemical agents analyzed by the flow cytometry mutation assay.

Several methods to assess genotoxicity of physical and chemical agents have been developed, most of which depend on growing colonies in selective medium. We recently published a new method for detecting mutations in the CD59 gene in a Chinese hamster ovary cell line that contains a single copy of human chromosome 11 (CHO A(L)). The assay is based on detecting the surface expression of CD59 with monoclonal antibodies using flow cytometry. The capabilities of this flow cytometry mutation assay (FCMA) to detect mutations from a wide variety of genotoxic agents are described here. There was a 400-fold separation between CD59- and CD59+ populations based on fluorescence intensity. Small numbers of negative cells mixed in with positive cells were detected in a highly linear fashion. Mutation dose response curves over a dose range yielding 80% to 20% survival are shown for ethyl methane sulfonate (EMS), mitomycin C (MMC) and lead acetate. EMS and lead acetate exhibited a threshold in response while MMC had a linear dose response over the full dose range. The mutant fraction was measured over time periods ranging up to 35 days following treatment. The mutant fraction peaked at different times ranging from 6 to 12 days after treatment. An additional 14 chemical and physical agents including point mutagens, heavy metals, ionizing and UV radiation, and DNA intercalators and cross linkers, were analyzed for mutagenic potential after doses giving 80% to 20% survival. The results presented here demonstrate the sensitivity and broad-ranging capability of the FCMA to detect mutations induced by a variety of genotoxic agents.

Animals↗
PubMed2006

Cell cycle dependent apoptosis and cell cycle blocks induced by hyperthermia in HL-60 cells.

The effects of heat are strongly dependent on the time of heating at a given temperature. The relationship between treatment time and temperature for a biological isoeffect (the Arrhenius plot) has been confirmed for a variety of normal tissues and tumours. A marked change of slope occurs somewhere between 42-43 degrees C. Above this transition temperature the slope is constant for a variety of cells and tissues. Therefore, when defining thermal doses in hyperthermia studies, both the time and temperature of heating are equally important determinants. In this study, cell cycle progression and apoptosis were analysed in HL-60 cells after heating from 5-60 min at 45.0 degrees C and also heating with five different iso-dose time-temperature heat treatments. A heat shock of 5-15 min at 45.0 degrees C caused the accumulation of cells in G1 and G2/M phases after 12 h at 37 degrees C, whereas a heat shock of 20-60 min at 45.0 degrees C reduced the number of non-apoptotic cells in all phases because the number of apoptotic cells increased. The fraction of apoptotic cells followed a sigmoid curve as the heating time increased from 5-60 min at 45.0 degrees C. Cell cycle analysis showed that apoptosis occurred predominantly in S-phase cells for shorter heating times but in all phases at longer times. An isodose heat shock lower than 44.0 degrees C (42.0-43.0 degrees C) gave the same apoptotic index, while heat shock from 44.0-46.0 degrees C caused a greater than expected apoptotic index. Thus, there was a transition at 44.0 degrees C in HL-60 cells, above which apoptosis increased rapidly. These results indicate that isodose analysis based on clonogenic survival in fibroblast cells may not be relevant for cell types which readily undergo apoptosis. Clonogenic survival was also compared with apoptosis for HL-60 cells and an apoptotic-resistant derivative cell line, HWC-2, heated for various times at 45.0 degrees C. Survival based on a clonogenic assay was much lower than survival based only on apoptotic index at all times for HL-60 cells. HWC-2 cells did not undergo apoptosis and also had a higher clonogenic survival than HL-60 cells.

Apoptosis↗
PubMed2005

NBS1 knockdown by small interfering RNA increases ionizing radiation mutagenesis and telomere association in human cells.

Hypomorphic mutations which lead to decreased function of the NBS1 gene are responsible for Nijmegen breakage syndrome, a rare autosomal recessive hereditary disorder that imparts an increased predisposition to development of malignancy. The NBS1 protein is a component of the MRE11/RAD50/NBS1 complex that plays a critical role in cellular responses to DNA damage and the maintenance of chromosomal integrity. Using small interfering RNA transfection, we have knocked down NBS1 protein levels and analyzed relevant phenotypes in two closely related human lymphoblastoid cell lines with different p53 status, namely wild-type TK6 and mutated WTK1. Both TK6 and WTK1 cells showed an increased level of ionizing radiation-induced mutation at the TK and HPRT loci, impaired phosphorylation of H2AX (gamma-H2AX), and impaired activation of the cell cycle checkpoint regulating kinase, Chk2. In TK6 cells, ionizing radiation-induced accumulation of p53/p21 and apoptosis were reduced. There was a differential response to ionizing radiation-induced cell killing between TK6 and WTK1 cells after NBS1 knockdown; TK6 cells were more resistant to killing, whereas WTK1 cells were more sensitive. NBS1 deficiency also resulted in a significant increase in telomere association that was independent of radiation exposure and p53 status. Our results provide the first experimental evidence that NBS1 deficiency in human cells leads to hypermutability and telomere associations, phenotypes that may contribute to the cancer predisposition seen among patients with this disease.

Apoptosis↗
PubMed2005

Effect of a membrane-targeted sphingosine kinase 1 on cell proliferation and survival.

Numerous extracellular stimuli activate SK1 (sphingosine kinase type 1) to catalyse the production of sphingosine 1-phosphate, a bioactive lipid that functions as both an extracellular ligand for a family of G-protein-linked receptors and as a putative intracellular messenger. Phorbol esters, calcium or immunoglobulin receptors stimulate SK1 by promoting its translocation to the plasma membrane, which brings it into proximity both to its substrate (i.e. sphingosine) and to activating acidic phospholipids (e.g. phosphatidylserine). To evaluate the consequence of SK translocation, we generated an SK1-derivative tagged with a myristoylation sequence (Myr-SK1) on its N-terminus and overexpressed the construct in 3T3-L1 fibroblasts using recombinant retrovirus. Myr-SK1 overexpression increased SK activity by more than 50-fold in crude membranes, while only stimulating cytoplasmic SK activity by 4-fold. In contrast, the overexpression of WT-SK1 (wild-type SK1), as well as that of a construct containing a false myristoylation sequence (A2-Myr-SK1), markedly increased SK activity in both membrane and cytoplasmic compartments. Immunofluorescence confirmed that Myr-SK1 preferentially localized at the plasma membrane, whereas WT-SK1 and A2-Myr-SK1 partitioned in cytoplasmic/perinuclear cellular regions. Surprisingly, Myr-SK1 overexpression significantly decreased the rates of cell proliferation by delaying exit from G0/G1 phase. Moreover, expression of Myr-SK1 but not WT-SK1 or A2-Myr-SK1 protected cells from apoptosis induced by serum withdrawal. Collectively, these findings reveal that altering the subcellular location of SK1 has marked effects on cell function, with plasma membrane-associated SK having a potent inhibitory effect on the G1-S phase transition.

3T3-L1 Cells↗
PubMed2005

Assay to measure CD59 mutations in CHO A(L) cells using flow cytometry.

BACKGROUND: A sensitive mammalian cell mutation assay was developed previously using a Chinese hamster ovary cell line (CHO A(L)) that stably incorporates human chromosome 11. The assay measures mutations in the CD59 gene on chromosome 11 but it requires the use of rabbit complement and colony growth for mutant selection. We have developed a more rapid flow cytometry-based mutation assay with CHO A(L) cells that uses monoclonal antibodies against CD59 to detect mutants and does not require colony formation. METHODS: CHO A(L) cells were treated with gamma-radiation or N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) and then allowed to grow for various times for mutant expression. Cells were labeled with monoclonal antibodies against CD59 and analyzed by flow cytometry. RESULTS: Negative and positive populations were separated by over 100-fold. Mixing various proportions of CD59-positive and -negative cells demonstrated that the assay is highly linear (r2 = 0.9999) and sensitive (<0.05% background mutants). The yield of CD59-inducible mutants was linearly related to dose for a clastogen (gamma-radiation) and point mutagen (MNNG). The mutant yield was time and treatment specific. CONCLUSIONS: Mutations induced by genotoxic agents can be rapidly and sensitively measured in CHO A(L) cells using flow cytometry.

Animals↗
PubMed2005

Evaluation of West Nile virus education campaign.

We evaluated the 2003 Kansas West Nile virus public education campaign. Awareness was widespread but compliance was low. Spanish-speaking persons were poorly informed. Relevant factors included population segment variability, campaign content, media choice, and materials delivery methods.

Aged↗
PubMed2004

What providers and medicaid policymakers need to know about barriers to employment for people with disabilities.

Medicaid Buy-Ins provide a new and exciting opportunity for people with disabilities to engage in meaningful employment while maintaining Medicaid coverage. Through interviews with participants in the Kansas Medicaid Buy-In, we examined perceived external influences on the decision to acquire or increase employment by people with disabilities. Two major external barriers were identified. First, physicians, therapists and case workers had frequently discouraged participants from getting jobs or increasing employment levels. Difficulty accessing adequate and consistent medical care and/or medications through Medicaid was also an issue in preventing participants from being able to acquire or increase employment.

Adult↗
PubMed2003

Flow cytometric measurement of fluorescence (Förster) resonance energy transfer from cyan fluorescent protein to yellow fluorescent protein using single-laser excitation at 458 nm.

BACKGROUND: Use of distinct green fluorescent protein (GFP) variants permits the study of protein-protein interactions and colocalization in viable transfected cells by fluorescence (Förster) resonance energy transfer (FRET). Flow cytometry is a sensitive method to detect FRET. However, the typical dual-laser methods used in flow cytometric FRET assays are not generally applicable because they require a specialized krypton ultraviolet (UV) laser. The purpose of this work was to develop a flow cytometric method to detect FRET between cyan fluorescent protein (CFP; donor) and yellow fluorescent protein (YFP; acceptor) by using the 458-nm excitation from a single tunable argon-ion laser. METHODS: FUSE-binding protein (FBP) interacting repressor (FIR) and FBP are c-myc transcription factors and are known to interact physically. To examine their interaction within viable cells, FIR and the binding motif of FBP, the FBP central domain (FBPcd), were fused with CFP and YFP, respectively, and this pair of fluorescently-tagged proteins was used to detect FRET in vivo. Cells transfected with expression plasmids encoding a CFP-FIR fusion protein and YFP as a negative control, a CFP-YFP fusion protein as a positive control, or CFP-FIR and YFP-FBPcd fusion proteins were examined for FRET after excitation with a 458-nm line from a tunable argon-ion laser. FRET was measured as the ratio of YFP:CFP emission or as YFP emission at 564-606 nm. Conventional FRET using the 413-nm UV line from a krypton laser was examined for comparison. Fluorescence signals were separated with a customized optical filter configuration using 530-nm shortpass, 500-nm longpass, and 560-nm shortpass dichroics in addition to 488/30 nm (CFP), 530/30 nm (YFP), and 585/42 nm (FRET) bandpass filters. Further, a laser-scanning confocal microscopic photobleach technique was used to document that FRET occurred by showing that the intensity of donor CFP fluorescence increased after its acceptor YFP was photobleached. Steady-state spectrofluorometry was used to confirm and validate the results detected by flow cytometry. RESULTS: Upon excitation with the 458-nm line of the argon-ion laser, the enhancement of the acceptor YFP signal and the decrease of the CFP signal were easily detected in cells transfected with the CFP-YFP construct or CFP-FIR and YFP-FBPcd. Similarly, FRET was detected under these conditions when the YFP emission was assessed at 564-606 nm. A strong correlation was observed between the increase in the YFP:CFP ratio and the YFP emission detected at 564-606 nm, consistent with the conclusion that FRET was detected comparably by both methods. A conventional flow cytometric krypton UV-laser technique was also used to confirm that FRET occurred with the CFP-YFP fusion protein and from CFP-FIR --> YFP-FBPcd. FRET also was confirmed by a confocal photobleaching technique, in which donor CFP intensity was enhanced after its acceptor YFP was photobleached. The flow cytometric and confocal microscopic results were confirmed by spectrofluorometry. CONCLUSION: These results demonstrated the feasibility of flow cytometric detection of FRET signals from CFP to YFP by excitation with the 458-nm line from the tunable argon-ion laser. The method was as efficient as excitation with the krypton UV laser and therefore should make FRET a more generally available flow cytometric technique.

Argon↗
PubMed2003

The role of early newborn discharge legislation in influencing policy development: understanding the Kansas experience.

Early newborn discharge legislation began a movement in health policy towards incremental changes in how medical consumers receive services. While well intentioned, these initiatives may undermine national efforts to address problems through more comprehensive reform, while stifling smaller efforts to address the problems locally. This paper discusses early newborn discharge legislation in Kansas: its origins, apparent impact, and implications. Findings from a hospital survey and two-year follow-up suggest a minimal effect of the legislation on health services in the state. Though acute hospital care appeared to replace home-based programs in many hospitals we spoke with, the more longstanding impact of the legislation seems to have been its precedent in how health policy is now made.

Female↗
PubMed2002

Defining and measuring nursing productivity: a concept analysis and pilot study.

AIMS: The purpose of this article is fourfold. First we report a concept analysis of nursing productivity to show the complexity of the concept and its measurement. We then show how the concept analysis was used to design a method for measuring nursing productivity. Third, we describe how we used this measure in a pilot study of the impact of a differentiated Registered Nurse (RN) practice model on productivity. Finally, we identify the challenges encountered and present recommendations for nurse executives and researchers based on our findings. RATIONALE: We believe our experience can be useful to nurse executives and researchers who are interested in studying the impact of care delivery models on nursing productivity. DESIGN: We defined productivity as the ratio of output (patient care hours per patient day) to input (paid salary and benefit dollars). We conducted a pilot test using the productivity measure developed from the concept analysis to determine the effects of a differentiated RN practice model on patient, staff, and organizational outcomes. The purpose of the pilot study was to determine whether the data needed to measure productivity could be obtained from administrative databases and to develop the steps and process for the analysis. We analysed data by 2-week pay periods for two quarters prior to implementation of the differentiated nursing practice model and for two quarters after implementation to assess for changes in nursing productivity. RESULTS: Pilot testing showed that we could detect changes in productivity using this measurement approach. It also revealed several challenges in using administrative databases to measure productivity. CONCLUSIONS: We discuss these challenges with recommendations for both nurse executives and researchers. The most reasonable approach for operational decision-making is longitudinal monitoring of productivity by organizational units combined with indicators of quality of patient care.

Decision Making, Organizational↗
PubMed2002

Similarities and differences in choosing health plans.

BACKGROUND: Increasingly, consumers have multiple health insurance options. New information is being developed to help consumers with these choices. OBJECTIVES: To study similarities and differences in how the publicly and privately insured choose health plans. To explore the effect of traditional enrollment materials and reports developed by the Consumer Assessment of Health Plans Study (CAHPS) on consumers' perceptions and decision-making. RESEARCH DESIGN: Using data from eight CAHPS demonstrations, we tested for significant differences across consumers with employer-sponsored insurance, Medicaid, and Medicare. SUBJECTS: Approximately 10,000 consumers with employer-sponsored, Medicaid, and Medicare health plans. MEASURES: Perceptions of the health plan selection process, use of information sources, and reactions to and use of traditional enrollment materials and CAHPS reports. RESULTS: Most consumers with all types of insurance thought that choosing a health plan was important and obtained information from multiple sources. Choosing a plan was more difficult for Medicare and Medicaid recipients than for the privately insured. When choosing a plan, Medicaid recipients cared most about convenience and access, whereas the privately insured emphasized providers and costs. The percentage of consumers who looked at and remembered the CAHPS report varied widely from 24% to 77%. In all but one of the demonstration sites, most consumers spent less than 30 minutes looking at the CAHPS report. CONCLUSIONS: Group sponsors and the developers of information interventions such as CAHPS may need to invest in developing and testing different reporting approaches for Medicare, Medicaid, and privately insured consumers.

Consumer Advocacy↗
PubMedDate not supplied

Evaluating a Medicaid home and community-based physical disability waiver.

State Medicaid waivers have fostered innovative health delivery systems for persons with special needs. Yet their overall cost effectiveness remains poorly understood. Changes were recently analyzed in Medicaid health services and costs for persons newly enrolled in the Kansas Physical Disability (PD) Waiver and found that ambulatory services increased, consistent with meeting enrollees' unmet medical needs and their access to enriched services. Home health, transportation, and personal care services also rose. Though not significant, hospital inpatient, outpatient, and long-term care services declined. This movement towards community-based service use in the short term reflects improved self-directed care and possible long-term cost savings.

Adult↗
PubMedDate not supplied

The effect of health communications on a statewide West Nile Virus public health education campaign.

OBJECTIVES: To determine knowledge, behavior, and attitude among Kansas residents exposed to a statewide West Nile Virus health education campaign. METHODS: Telephone survey employing random selection of urban and rural counties and telephone numbers. RESULTS: Knowledge was widespread, preventive behaviors less so. TV, newspapers, and word-of-mouth were most frequently cited sources of information. A small percentage of individuals received information from health professionals. CONCLUSIONS: Recommendations are made for designing and implementing future campaigns, including taking into account target population demographics, populations at highest risk, and channels of communication. Greater use of the Internet, word of mouth, and newspapers appear most promising.

Adolescent↗