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Biomedical subjects

D E Nelson

Publications and source records attributed to D E Nelson.

At least 19 recordsLinked to original sources
PubMed2006

Chlamydophila pneumoniae and human cytomegalovirus in atherosclerotic carotid plaques--combined presence and possible interactions.

The aim of our study was to investigate the combination of Chlamydophila pneumoniae and human cytomegalovirus (HCMV) as a pathogenic factor in atherosclerosis. Accordingly, we tested by means of PCR and immunohistochemistry the presence of these pathogens in the same atherosclerotic carotid specimen. The histology of the samples and the patients' antibodies against these pathogens were evaluated. Further, we examined the impact of C. pneumoniae and HCMV infection on the gene expression of the human monocytic cell line U937. Six of the 22 samples contained only C. pneumoniae, 4 contained only HCMV, 7 contained both C. pneumoniae DNA and/or antigens of both pathogens, and 5 samples were negative. No correlation was found between the presence of these microbes and either the cellular structure of the plaques, or the serostatus of the patients. The infection of U937 cells with HCMV and especially C. pneumoniae induced inflammation and atherosclerosis-related genes. Furthermore, the doubly-infected cells produced higher levels of the mRNA of pro-platelet basic protein and fatty acid binding protein 4. In conclusion, C. pneumoniae is often present in combination with HCMV in atherosclerotic carotid lesions. The in vitro coinfection model reveals that the doubly-infected monocytes are potent expressors of proatherosclerotic genes, suggesting that this coinfected population may accelerate the process of atherosclerosis.

Aged↗
PubMed2004

Oscillations in NF-kappaB signaling control the dynamics of gene expression.

Signaling by the transcription factor nuclear factor kappa B (NF-kappaB) involves its release from inhibitor kappa B (IkappaB) in the cytosol, followed by translocation into the nucleus. NF-kappaB regulation of IkappaBalpha transcription represents a delayed negative feedback loop that drives oscillations in NF-kappaB translocation. Single-cell time-lapse imaging and computational modeling of NF-kappaB (RelA) localization showed asynchronous oscillations following cell stimulation that decreased in frequency with increased IkappaBalpha transcription. Transcription of target genes depended on oscillation persistence, involving cycles of RelA phosphorylation and dephosphorylation. The functional consequences of NF-kappaB signaling may thus depend on number, period, and amplitude of oscillations.

Active Transport, Cell Nucleus↗
PubMed2004

Oscillations in transcription factor dynamics: a new way to control gene expression.

Oscillations in second-messenger signalling (e.g. calcium) have previously been shown to be important in the control of transcription. More recently, oscillations in localization and absolute levels of transcription factors and their regulators have been identified. Here we discuss the role of network motifs such as the negative feedback loop and their role in oscillatory signalling, and how oscillations in components of the nuclear factor kappaB signalling pathway are important to the dynamic control of transcription in response to a cytokine stimulus.

Animals↗
PubMed2003

Alpha-1-antitrypsin expression in the lung is increased by airway delivery of gene-transfected macrophages.

Inadequate antiprotease activity in the lungs due to alpha-1-antitrypsin (A1AT) deficiency is a factor of early-onset emphysema. We propose a new approach to gene therapy that involves the intratracheal delivery of macrophages expressing human A1AT (hA1AT). Recombinant adeno-associated virus (rAAV) plasmids encoding the hA1AT gene were packaged into virions using 293 cells, and transgenic progeny virus was purified from the cells. The murine macrophage cell line J774A.1 was infected in vitro with the recombinant hA1AT rAAV virus. The hA1AT-producing macrophages were delivered intratracheally into mechanically ventilated C57BL/6J mice, a strain with low endogenous levels of A1AT. Transcription of hA1AT mRNA was detected in the transfected cells by RT-PCR, and protein expression was verified by immunohistochemistry. Levels of hA1AT in the cell culture medium and in the bronchoalveolar lavage (BAL) were assayed by ELISA. The concentration of hA1AT in J774A.1 cell-conditioned medium increased from undetectable levels prior to transfection, to 60 mg/l at 24 h post-transfection. At 1, 3 and 7 days after intratracheal delivery of transfected macrophages, hA1AT protein in BAL from C57BL/6J mice increased from undetectable levels to 2.5+/-0.9, 2.6+/-1.1 and 2.2+/-0.8 mg/l, respectively. These results suggest that airway delivery of macrophages overexpressing hA1AT may be an effective approach to enhance alveolar protection in A1AT deficiency.

Administration, Inhalation↗
PubMed2001

Contributions of PBP 5 and DD-carboxypeptidase penicillin binding proteins to maintenance of cell shape in Escherichia coli.

Escherichia coli has 12 recognized penicillin binding proteins (PBPs), four of which (PBPs 4, 5, and 6 and DacD) have DD-carboxypeptidase activity. Although the enzymology of the DD-carboxypeptidases has been studied extensively, the in vivo functions of these proteins are poorly understood. To explain why E. coli maintains four independent loci encoding enzymes of considerable sequence identity and comparable in vitro activity, it has been proposed that the DD-carboxypeptidases may substitute for one another in vivo. We tested the validity of this equivalent substitution hypothesis by investigating the effects of these proteins on the aberrant morphology of DeltadacA mutants, which produce no PBP 5. Although cloned PBP 5 complemented the morphological phenotype of a DeltadacA mutant lacking a total of seven PBPs, controlled expression of PBP 4, PBP 6, or DacD did not. Also, a truncated PBP 5 protein lacking its amphipathic C-terminal membrane binding sequence did not reverse the morphological defects and was lethal at low levels of expression, implying that membrane anchoring is essential for the proper functioning of PBP 5. By examining a set of mutants from which multiple PBP genes were deleted, we found that significant morphological aberrations required the absence of at least three different PBPs. The greatest defects were observed in cells lacking, at minimum, PBPs 5 and 6 and one of the endopeptidases (either PBP 4 or PBP 7). The results further differentiate the roles of the low-molecular-weight PBPs, suggest a functional significance for the amphipathic membrane anchor of PBP 5 and, when combined with the recently determined crystal structure of PBP 5, suggest possible mechanisms by which these PBPs may contribute to maintenance of a uniform cell shape in E. coli.

Bacterial Proteins↗
PubMed2001

Reconstruction of Escherichia coli mrcA (PBP 1a) mutants lacking multiple combinations of penicillin binding proteins.

Previously, we constructed a set of mutants from which eight penicillin binding protein (PBP) genes were deleted in 192 combinations from Escherichia coli (S. A. Denome, P. K. Elf, T. A. Henderson, D. E. Nelson, and K. D. Young, J. Bacteriol. 181:3981-3993, 1999). Although these mutants were constructed correctly as determined by restriction mapping and the absence of relevant protein products, we recently discovered by PCR mapping that strains from which mrcA (PBP 1a) was deleted were also missing two neighboring genes of unknown function (yrfE and yrfF). We created a new deletion mutation in mrcA and reconstructed 63 strains lacking PBP 1a and other PBP mutant combinations. The new mrcA mutants do not exhibit mucoidy, phage resistance, temperature sensitivity, growth rate defects, or antibiotic resistance, suggesting that these phenotypes require the loss of either yrfE or yrfF alone or in combination with the absence of multiple PBPs.

Bacterial Proteins↗
PubMed2001

Reliability and validity of measures from the Behavioral Risk Factor Surveillance System (BRFSS).

OBJECTIVES: To assess the reliability and validity of measures on the BRFSS, to assist users in evaluating the quality of BRFSS data, and to identify areas for further research. METHODS: Review and summary of reliability and validity studies of measures on the BRFSS and studies of measures that were the same or similar to those on the BRFSS from other surveys. RESULTS: Measures determined to be of high reliability and high validity were current smoker, blood pressure screening, height, weight, and BMI, and several demographic characteristics. Measures of both moderate reliability and validity included when last mammography was received, clinical breast exam, sedentary lifestyle, intense leisure-time physical activity, and fruit and vegetable consumption. Few measures were of low validity and only one measure was determined to be of low reliability. Several other measures were of high or moderate reliability or validity, but not both. The reliability or validity could not be determined for some measures, primarily due to lack of research. CONCLUSIONS: Most questions on the core BRFSS instrument were at least moderately reliable and valid, and many were highly reliable and valid. Additional research is needed for some measures.

Adult↗
PubMed2000

Validation of self-reported chronic conditions and health services in a managed care population.

BACKGROUND: Self-reported data are commonly used to estimate the prevalence of health conditions and the use of preventive health services in the population, but the validity of such data is often questioned. METHODS: The Behavioral Risk Factor Survey (BRFS) was admin istered by telephone to a stratified, random sample of health maintenanc e organization (HMO) subscribers in Colorado in 1993, and self-reports w ere compared with HMO medical records for 599 adults aged >21. Sensitivity and specificity were calculated for three chronic conditions and use of six preventive services. RESULTS: Sensitivity was highest for hypertension (83%), moderate for diabetes (73%), and lowest for hypercholesterolemia (59%); specificity was >80% for all three conditions. Sensitivity ranged from 86% to 99% for influenza immunization, clinical breast examination, blood cholesterol screening, mammography, Pap test, and blood pressure screening; specificity was <75% for all preventive services. CONCLUSIONS: Self-reports are reasonably accurate for certain chronic conditions and for routine screening exams and can provide a useful estimate for broad measures of population prevalence.

Adult↗
PubMed2000

Na+/myo-inositol symporters and Na+/H+-antiport in Mesembryanthemum crystallinum.

Mitr1 and Mitr2 from Mesembryanthemum crystallinum (common ice plant) are members of a family of genes homologous to H+[or Na+]/myo-inositol symporters (ITRs), not previously studied in plants. MITR1 complemented an Itr1-deficient yeast strain. Mitr1 is strongly expressed in roots, moderately in stems, and weakly in leaves. Its transcripts increased in all organs, most dramatically in roots, under salinity stress. Mitr2 constitutes a rare transcript, slightly upregulated by salt stress in leaves only. Mitr1 transcripts are present in all cells in the root tip, but become restricted to phloem-associated cells in mature roots. Peptide antibodies against the two proteins indicated the presence of MITR1 in all organs and of MITR2 in leaves. Both are located in the tonoplast. MITR1 acts in removing sodium from root vacuoles, correlated with findings of low root sodium, while leaf vacuoles accumulate sodium in the ice plant. Up-regulation in leaves and stems is also found for Na+/H+-antiporter (Nhx-type) transcripts. Under comparable stress conditions, Nhx-and Itr-like transcripts in Arabidopsis were regulated differently. In the ice plant, co-ordinate induction of Na+/H+-antiporters and Na+/myo-inositol symporters transfers sodium from vacuoles in root cells into the leaf mesophyll as a halophytic strategy that lowers the osmotic potential. The tissue-specific differential expression of Itr- and Nhx-type transcripts suggests that the vacuolar sodium/inositol symporters function to reduce sodium amounts in cells of the root and vascular tissue, while sodium/proton antiporters in leaf tissues function to partition sodium into vacuoles for storage.

Amino Acid Sequence↗
PubMed2000

Penicillin binding protein 5 affects cell diameter, contour, and morphology of Escherichia coli.

Although general physiological functions have been ascribed to the high-molecular-weight penicillin binding proteins (PBPs) of Escherichia coli, the low-molecular-weight PBPs have no well-defined biological roles. When we examined the morphology of a set of E. coli mutants lacking multiple PBPs, we observed that strains expressing active PBP 5 produced cells of normal shape, while mutants lacking PBP 5 produced cells with altered diameters, contours, and topological features. These morphological effects were visible in untreated cells, but the defects were exacerbated in cells forced to filament by inactivation of PBP 3 or FtsZ. After filamentation, cellular diameter varied erratically along the length of individual filaments and many filaments exhibited extensive branching. Also, in general, the mean diameter of cells lacking PBP 5 was significantly increased compared to that of cells from isogenic strains expressing active PBP 5. Expression of cloned PBP 5 reversed the effects observed in DeltadacA mutants. Although deletion of PBP 5 was required for these phenotypes, the absence of additional PBPs magnified the effects. The greatest morphological alterations required that at least three PBPs in addition to PBP 5 be deleted from a single strain. In the extreme cases in which six or seven PBPs were deleted from a single mutant, cells and cell filaments expressing PBP 5 retained a normal morphology but cells and filaments lacking PBP 5 were aberrant. In no case did mutation of another PBP produce the same drastic morphological effects. We conclude that among the low-molecular-weight PBPs, PBP 5 plays a principle role in determining cell diameter, surface uniformity, and overall topology of the peptidoglycan sacculus.

Aztreonam↗
PubMed2000

Light pulses suppress responsiveness within the mouse photic entrainment pathway.

We have characterized a decrease in photic responsiveness of the mammalian circadian entrainment pathway caused by light stimulation. Phase delays of the running-wheel activity rhythm were used to quantify the photic responsiveness of the circadian system in mice (C57BL/6J). In an initial experiment, the authors measured the responsiveness to single "saturating" light pulses ("white" fluorescent light; approximately 1876 [microW; 15 min). In two additional experiments, the authors measured responses to this stimulus at several time points following a saturating pulse at CT 14 or CT 16. Data from these experiments were analyzed in two manners. Experiment 2 was analyzed assuming that the phase of the circadian pacemaker was unchanged by an initial pulse, and Experiment 3 was analyzed assuming that the initial pulse induced an instantaneous phase delay. Results reveal a significant reduction in responsivity to light that persists for at least 2 h and possibly up to 4 h after the initial stimulus. Immediately after the stimulus, the responsiveness of the photic entrainment pathway was reduced to levels < or = 12% of normal. After 2 h, the responsiveness was < or = 42% of normal, and by 4 h, responsiveness had recovered to levels that were < or = 60% of normal (levels not statistically different from controls). By the following circadian cycle, responsiveness was more completely recovered, although the magnitude of some phase delays remained < or = 85% of normal. These major reductions in the magnitude of phase delays (and phase response curve amplitude) caused by saturating light pulses confound interpretations of two-pulse experiments designed to measure the rate of circadian phase delays. In addition, the time course for this reduced responsiveness may reflect the time course of cellular and molecular events that underlie light-induced resetting of the mammalian circadian pacemaker.

Animals↗
PubMed2000

Uses of Behavioral Risk Factor Surveillance System data, 1993-1997.

OBJECTIVES: The purpose of this study was to document and describe Behavioral Risk Factor Surveillance System (BRFSS) data use patterns, benefits, and barriers from 1993 to 1997. METHODS: Data use information was gathered via a Medline database search and a telephone survey of BRFSS program directors (n = 54). RESULTS: The database search uncovered 109 BRFSS-based reports. Program directors indicated that BRFSS data frequently were used to support health policies regarding diabetes, physical activity, and smoking. Frequent data use barriers included insufficient special population data, insufficient city- or county-specific data, and insufficient staff. CONCLUSIONS: Use of BRFSS data, which aid several state health activities, increased from 1993 to 1997.

Data Interpretation, Statistical↗
PubMed2000

What people really know about their health insurance: a comparison of information obtained from individuals and their insurers.

OBJECTIVES: This study determined the validity of self-reported data on selected health insurance characteristics. METHODS: We obtained telephone survey data on the presence of health insurance, source of insurance, length of time insured, and type of insurance (managed care or fee-for-service) from a random sample of 351 adults in 3 Wisconsin counties and compared findings with data from respondents' health insurers. RESULTS: More than 97% of the respondents correctly reported that they were currently insured. For source of insurance among persons aged 18 to 64 years, sensitivity was high for those covered through private health insurance (93.8%) but low for those covered through public insurance (6.7%). Only 33.1% of the respondents accurately categorized length of enrollment in their current plan. Overall estimates for managed care enrollment were similar for the 2 sources, but individual validity was low: 84.2% of those in fee-for-service believed that they were in managed care. CONCLUSIONS: Information obtained from the general population about whether they have health insurance is valid, but self-reported data on source of insurance, length of time insured, and type of insurance are suspect and should be used cautiously.

Adolescent↗
PubMed2000

Diabetes trends in the U.S.: 1990-1998.

OBJECTIVE: To examine trends in diabetes prevalence in the U.S. RESEARCH DESIGN AND METHODS: This study was conducted via telephone surveys in states that participated in the Behavioral Risk Factor Surveillance System between 1990 and 1998. The participants consisted of noninstitutionalized adults aged 18 years or older. The main outcome measure was self-reported diabetes. RESULTS: The prevalence of diabetes rose from 4.9% in 1990 to 6.5% in 1998--an increase of 33%. Increases were observed in both sexes, all ages, all ethnic groups, all education levels, and nearly all states. Changes in prevalence varied by state. The prevalence of diabetes was highly correlated with the prevalence of obesity (r = 0.64, P<0.001). CONCLUSIONS: The prevalence of diabetes continues to increase rapidly in the U.S. Because the prevalence of obesity is also rising, diabetes will become even more common. Major efforts are needed to alter these trends.

Adult↗
PubMed1999

Household firearm storage practices: do responses differ by whether or not individuals ever use firearms?

INTRODUCTION: The prevalence with which firearms are stored loaded or unlocked has been measured in previous surveys. Our purpose was to compare household firearm storage practices reported by firearm users and nonusers. METHODS: We analyzed telephone survey data from the 1992 and 1993 Oregon Behavioral Risk Factor Surveillance System on 2454 randomly selected adults in households with firearms. We compared reported firearm storage practices among persons who ever used firearms with persons who had never used firearms by demographics and type of firearm. RESULTS: Nonusers of firearms were much less likely than firearm users to report that household firearms were always or sometimes stored loaded [odds ratio (OR) = 0.45, 95% confidence interval (CI):0.36-0.54] or stored loaded and unlocked (OR = 0.46, 95% CI: 0.36-0.57). Except for persons aged 18 to 34 years and persons in handgun-only households, differences in reported firearm storage practices between nonusers and users varied little by demographic characteristics or by type of firearm. Nonusers of household firearms may be unaware that firearms are stored loaded or stored loaded and unlocked in their homes. CONCLUSIONS: Surveys that do not consider firearm use status may underestimate household exposure to loaded firearms or to loaded and unlocked firearms.

Accidents, Home↗
PubMed1999

Escherichia coli mutants lacking all possible combinations of eight penicillin binding proteins: viability, characteristics, and implications for peptidoglycan synthesis.

The penicillin binding proteins (PBPs) synthesize and remodel peptidoglycan, the structural component of the bacterial cell wall. Much is known about the biochemistry of these proteins, but little is known about their biological roles. To better understand the contributions these proteins make to the physiology of Escherichia coli, we constructed 192 mutants from which eight PBP genes were deleted in every possible combination. The genes encoding PBPs 1a, 1b, 4, 5, 6, and 7, AmpC, and AmpH were cloned, and from each gene an internal coding sequence was removed and replaced with a kanamycin resistance cassette flanked by two res sites from plasmid RP4. Deletion of individual genes was accomplished by transferring each interrupted gene onto the chromosome of E. coli via lambda phage transduction and selecting for kanamycin-resistant recombinants. Afterwards, the kanamycin resistance cassette was removed from each mutant strain by supplying ParA resolvase in trans, yielding a strain in which a long segment of the original PBP gene was deleted and replaced by an 8-bp res site. These kanamycin-sensitive mutants were used as recipients in further rounds of replacement mutagenesis, resulting in a set of strains lacking from one to seven PBPs. In addition, the dacD gene was deleted from two septuple mutants, creating strains lacking eight genes. The only deletion combinations not produced were those lacking both PBPs 1a and 1b because such a combination is lethal. Surprisingly, all other deletion mutants were viable even though, at the extreme, 8 of the 12 known PBPs had been eliminated. Furthermore, when both PBPs 2 and 3 were inactivated by the beta-lactams mecillinam and aztreonam, respectively, several mutants did not lyse but continued to grow as enlarged spheres, so that one mutant synthesized osmotically resistant peptidoglycan when only 2 of 12 PBPs (PBPs 1b and 1c) remained active. These results have important implications for current models of peptidoglycan biosynthesis, for understanding the evolution of the bacterial sacculus, and for interpreting results derived by mutating unknown open reading frames in genome projects. In addition, members of the set of PBP mutants will provide excellent starting points for answering fundamental questions about other aspects of cell wall metabolism.

Bacterial Proteins↗