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Biomedical subjects

C C Davis

Publications and source records attributed to C C Davis.

At least 19 recordsLinked to original sources

A toroid model for in vitro investigations of toxic shock syndrome toxin-1 production.

Human behaviours and consumer products may affect vaginal microbial ecology, thereby influencing women's health. Relevant experimentation systems are needed to understand such possible links. Here, we describe the development of a practical semi-solid in vitro model to assess the effects of interactions between vaginal environment and the presence of tampons, on bacterial communities, including the production of toxic shock syndrome toxin-1 (TSST-1) by Staphylococcus aureus.

Bacterial Toxins↗

Is serum leptin related to physical function and is it modifiable through weight loss and exercise in older adults with knee osteoarthritis?

OBJECTIVE: To determine the effect of weight loss and exercise interventions on serum leptin and to investigate the relationship of physical function and osteoarthritis (OA) severity with serum leptin in older overweight and obese adults with knee OA. In addition, the study examined if serum leptin predicts weight loss. DESIGN: Longitudinal, controlled clinical trial of weight loss and exercise interventions. SUBJECTS: Community dwelling, older, overweight and obese adults (n=316; >60 years of age; body mass index >/=28.0 kg m(-2)) with symptomatic knee OA and self-reported difficulty in performing selected physical activities were recruited. INTERVENTIONS: Participants were randomized into one of four groups for the 18-month study duration: Healthy Lifestyle Controls, Dietary Weight Loss (Diet), Exercise Training (Exercise), and a combination of Dietary Weight Loss and Exercise Training (Diet+Exercise). The weight loss goal for the two Diet groups was 5% from baseline at 18 months. Participants in the Exercise groups were trained for 3 days week(-1), 60 min day(-1). MEASUREMENTS: Body weight, body mass index, serum leptin, physical function, and OA severity were measured at baseline, 6 months, and 18 months. RESULTS: Diet and Diet+Exercise groups lost 5.3 and 6.1% of their weight, respectively, at 18 months with the Exercise group losing 2.9%. There was a significant main effect of weight loss on serum leptin with a decrease in serum leptin averaged across the 6- and 18-month time points for the Diet and Diet+Exercise groups compared to the other two groups (beta=0.245; P<0.01). No main effect for exercise training was observed. Serum leptin was related to self-reported physical function. In all participants, a mixed model analysis demonstrated that lower levels of baseline serum leptin predict larger weight loss (beta=-2.779; P=0.048). CONCLUSION: Decreases in serum leptin may be one mechanism by which weight loss improves physical function and symptoms in OA patients.

Aged↗

Comparative molecular analysis of community- or hospital-acquired methicillin-resistant Staphylococcus aureus.

Community-acquired methicillin-resistant Staphylococcus aureus (CA-MRSA) is a growing public health concern that has been associated with pediatric fatalities. It is hypothesized that the evolution of CA-MRSA is a recent event due to the acquisition of mec DNA by previously methicillin-susceptible strains that circulated in the community. This study investigated the genetic relatedness between CA-MRSA, hospital-associated MRSA (HA-MRSA), and nonmenstrual toxic shock syndrome (nmTSS) isolates. Thirty-one of 32 CA-MRSA isolates were highly related as determined by pulsed-field gel electrophoresis and spa typing yet were distinguishable from 32 HA-MRSA strains. The 31 related CA-MRSA isolates produced either staphylococcal enterotoxin B (n = 5) or C (n = 26), and none made TSS toxin 1. All CA-MRSA isolates tested contained a type IV staphylococcal cassette chromosome mec (SCCmec) element. In comparison, none of the HA-MRSA isolates (n = 32) expressed the three superantigens. Antibiotic susceptibility patterns were different between the CA-MRSA and HA-MRSA isolates; CA-MRSA was typically resistant only to beta-lactam antibiotics. Six of twenty-one nmTSS isolates were indistinguishable or highly related to the CA-MRSA isolates. MnCop, an nmTSS isolate obtained in Alabama in 1986, was highly related to the CA-MRSA isolates except that it did not contain an SCCmec element. These data suggest that CA-MRSA strains may represent a new acquisition of SCCmec DNA in a previously susceptible genetic background that was capable of causing nmTSS. CA-MRSA poses a serious health risk not only because it is resistant to the antibiotics of choice for community-acquired staphylococcal infections but also because of its ability to cause nmTSS via superantigen production.

Community-Acquired Infections↗

Single-photon tunneling via localized surface plasmons.

Strong evidence of a single-photon tunneling effect, a direct analog of single-electron tunneling, has been obtained in the measurements of light tunneling through individual subwavelength pinholes in a gold film covered with a layer of polydiacetylene. The transmission of some pinholes reached saturation because of the optical nonlinearity of polydiacetylene at a very low light intensity of a few thousand photons per second. This result is explained theoretically in terms of a "photon blockade," similar to the Coulomb blockade phenomenon observed in single-electron tunneling experiments. Single-photon tunneling may find applications in the fields of quantum communication and information processing.

Journal Article↗

High resolution study of permanent photoinduced reflectivity changes and charge-order domain switching in Bi(0.3)Ca(0.7)MnO(3).

We report near-field and far-field optical microscopic studies of photoinduced effects in charge-ordered Bi(0.3)Ca(0.7)MnO(3). Unlike previously reported transient photoinduced effects in manganites, we have observed permanent reflectivity changes following local sample illumination with 488 nm light. High-resolution images of exposed regions reveal optical contrast on a submicrometer scale. This observation indicates that photonic band-gap structures may be created using holographic recording in manganites. We also present images of photoinduced charge-order domain switching in Bi(0.3)Ca(0.7)MnO(3).

Journal Article↗

Implications of aqueous silica sorption to iron hydroxide: mobilization of iron colloids and interference with sorption of arsenate and humic substances.

This work highlighted practical implications of aqueous silica sorption to iron hydroxide in natural and engineered systems. Two types of surfaces were prepared by exposing 10 mg/L preformed Fe(OH)3 to aqueous silica (0-200 mg/L as SiO2) for periods of 1.5 h or 50 days. After 1.5 h, the concentration of iron passing through a 0.45 microm pore size filter at pH 6.0-9.5 was always negligible, but if zeta potential < or =-15 mV as much as 35% of the iron passed through filters after 50 days of aging. When arsenate was added to 10 mg/L iron hydroxide particles equilibrated with aqueous silica for 1.5 h, percentage arsenate removals were high. In contrast, if silica was preequilibrated with iron for 50 days, arsenate removals decreased markedly at higher pH and aqueous silica concentrations. Similar trends were observed for humic substances, although their removal was nearly completely prevented at pH 8.5 at SiO2 concentrations above 50 and 10 mg/L at 1.5 h and 50 days exposure, respectively. The mechanism of interference was hindered sorption to the iron hydroxide surface.

Arsenates↗

Nonparametric linkage regression. II: Identification of influential pedigrees in tests for linkage.

We applied case-deletion-based diagnostics to the combined Caucasian genome scan data for asthma and IgE from the Collaborative Study on the Genetics of Asthma (CSGA) and German family studies in order to identify influential pedigrees in tests for linkage. These methods identified 12 pedigrees whose data appear not to fit the asthma linkage model and for whom alternative genetic and nongenetic explanations can be explored. The methods also identified four pedigrees for chromosome 1 and two pedigrees for chromosome 2 that provide strong evidence for linkage at their respective loci. Similarly, these methods helped identify four pedigrees that strongly influenced the linkage tests for IgE. From these data, we can construct an enriched subset of pedigrees to be used in further analysis for mapping region-specific putative trait predisposing loci.

Adult↗

Nonparametric linkage regression. I: Combined Caucasian CSGA and German genome scans for asthma.

In this paper we applied the nonparametric linkage (NPL) regression approach to the combined Caucasian genome scan data from the Collaborative Study on the Genetics of Asthma (CSGA) and German family studies to search for regions of the genome that exhibit evidence for linkage to putative asthma-predisposing genes. The multipoint single-locus model identified three regions of the genome with LOD scores of approximately two or greater. These regions were on 6p near D6S291 (LOD = 2.78), 2p near D2S2298 (LOD = 2.11), and 1p near D1S1597 (LOD = 1.92). Modeling multiple loci together and testing for interactions among loci yielded stronger evidence for linkage in these regions. We observed a potential epistatic interaction between 2p and 14p (p = 0.0003) and conditional LOD scores of 2.75 on 1p, 3.89 on 6p, 1.64 on 7p, and 1.64 on 15q.

Adult↗

Near-field second harmonic imaging of the c/a/c/a polydomain structure of epitaxial PbZrxTi(1-x)O3 thin films.

Near-field optical second harmonic microscopy has been applied to imaging of the c/a/c/a polydomain structure of epitaxial PbZrxTi1-xO3 thin films in the 0 < x < 0.4 range. Comparison of the near-field optical images and the results of atomic force microscopy and X-ray diffraction studies show that an optical resolution of the order of 100 nm is achieved. Symmetry properties of the near-field second harmonic signal allow us to obtain good optical contrast between the local second harmonic generation in c- and a-domains. Experimentally measured near-field second harmonic images have been compared with the results of theoretical calculations. Good agreement between theory and experiment is demonstrated.

Journal Article↗

Why older community-dwelling adults do not discuss urinary incontinence with their primary care physicians.

OBJECTIVES: This study explored reasons why older adults with urinary incontinence (UI) do not initiate discussions with or seek treatment for UI from their primary care provider. DESIGN: A randomized, prospective controlled trial involving 41 primary care sites. SETTING: Primary care practice sites. PARTICIPANTS: 49 older adults age 60 and older not previously screened for UI by their primary care doctor. MEASUREMENTS: Demographic data, self-reported bladder-control information using questionnaires, and health status. RESULTS: Adults who did not discuss UI were older, had less-frequent leaking accidents and fewer nighttime voids and were less bothered by UI than those who did. The two main reasons why patients did not seek help were the perceptions that UI was not a big problem (45%) and was a normal part of aging (19%). CONCLUSIONS: Embarrassment or lack of awareness of treatment options were not significant barriers to discussing UI. Adults with a fairly high frequency of UI (average of 1.7 episodes per day) did not view UI as abnormal or a serious medical condition.

Aged↗

Evanescent wave long-period fiber bragg grating as an immobilized antibody biosensor.

An immunosensor using a long-period grating (LPG) was used for sensitive detection of antibody-antigen reactions. Goat anti-human IgG (antibody) was immobilized on the surface of the LPG, and detection of specific antibody-antigen binding was investigated. This sensor operates using total internal reflection where an evanescent field interacts with bound antibody immobilized over the grating region. The reaction between antibody and antigen altered the LPG transmission spectrum and was monitored in real time as a change in refractive index, thereby eliminating the need for labeling antigen molecules. Human IgG binding was observed to be concentration dependent over a range of 2-100 microg mL-1, and equilibrium bound antigen levels could be attained in approximately 5 min using an initial rate determination. Binding specificity was confirmed using human interleukin-2 and bovine serum albumin as controls, and nonspecific adsorption of proteins did not significantly interfere with detection of binding. Antigen detection in a heterogeneous protein mixture and in crude cell lysate from Escherichia coli was also confirmed. Moreover, regeneration of the LPG surface via diethylamine treatment resulted in approximately 80% removal of bound antigen. Subsequently, fibers reexposed to antigen retained greater than 85% of the initial signal after five consecutive regeneration cycles.

Animals↗

The association of depressive symptoms and urinary incontinence among older adults.

OBJECTIVES: To examine the relationship of urinary incontinence (UI) and depressive symptoms (DS) in older adults. DESIGN: A randomized, controlled trial to determine the effects of clinical practice guideline implementation on provider attitudes and behavior, and patients' UI, health status, quality of life, and satisfaction with care. Baseline and endpoint data were collected from patients via computer-assisted telephone interviewing. SETTING: Forty-one nonacademic primary care practices (PCP) in North Carolina. PARTICIPANTS: A total of 668 community-dwelling adults (age > 60) who had visited the one of the selected PCPs. INTERVENTION: PCPs in the intervention group were given instruction in the detection and management of UI, educational materials for providers and patients, office system supports, and academic detailing. MEASUREMENTS: The dependent measure was assessed using an eight-item screener for DS. UI (status, frequency, amount), health (physical, mental), and demographic (age, gender, marital status) and self-report information about bladder control served as predictors. RESULTS: Wilcoxon rank sum tests showed that UI status was associated with moderate to severe DS (43% vs 30%, P = .05). Multivariate analyses showed that UI status, physical and mental health, and gender were significant predictors of DS. Among UI adults (n = 230), physical and mental health, life satisfaction, and the perception that UI interfered with daily life were significant predictors of DS. CONCLUSIONS: This study provides clear evidence that UI is related to DS in older adults.

Age Distribution↗

Expression analysis of human HL60 cells exposed to 60 Hz square- or sine-wave magnetic fields.

A total of 960 complementary DNA (cDNA) clones from an HL60 cell cDNA library were screened to discover genes that were differentially expressed in HL60 cells exposed to 60 Hz square-wave magnetic fields (MFs) compared to sham-exposed cells. Square-wave fields are rich in odd harmonic frequency content. We used a two-gel cDNA library screening method (BIGEL) to identify treatment-induced alterations in gene expression. Four cDNA clones were tentatively identified as differentially expressed after exposure to square-wave MFs at 2 mT for 24 h. BIGEL-identified genes (GenBank accession number) corresponding to these clones were: TI227H (D50525), EST Homo sapiens partial cDNA (Z17814), human ribosomal protein S13 (L01124), and AICAR transformylase mRNAs (D82348). The differences in mRNA levels were not confirmed in test compared to experimental cells by Northern analysis. In other experiments, we used concurrent exposure to 60 Hz sine- or square-wave MFs (0 or 2 mT, duration of 3 or 24 h, no postexposure delay). In addition to the four BIGEL genes, we also investigated MYC, HSP70, RAN and SOD1. In the case of MYC and HSP70, square-wave MFs appeared to exhibit more marked alterations when compared to sinusoidal waveforms, but the overall results indicated no effect of possible differential magnetic-field-induced expression of all eight genes. In contrast, alterations of mRNA levels were observed for seven genes after exposure to X irradiation, hyperthermia and TPA. These results are contrary to previously proposed similarities between the action of these agents and MF effects on gene transcription.

Blotting, Northern↗

Food and Drug Administration low-level extremely-low-frequency magnetic field exposure facility.

We describe the design, construction details, and performance characteristics of an exposure system designed to provide very well controlled extremely-low-frequency magnetic field exposures of in vitro samples. This system uses Helmholtz coils placed inside temperature-controlled mu-metal chambers to provide simultaneous ac and dc field exposures at any relative angle with minimal residual background field. The system has both exposed and sham-exposed chambers and is operated under computer control in such a way as to ensure blind exposure of samples.

Animals↗

Tapered optical fiber sensor using near-infrared fluorophores to assay hybridization.

We present an all-fiber hybridization assay sensor that relies on the evanescent field excitation of fluorescence from surface-bound fluorophores. The evanescent field is made accessible through the use of a long, adiabatically tapered single-mode fiber probe. A laser diode with a 785-nm wavelength is used in a pulsed mode of operation to excite fluorescence in the tapered region of a fiber probe using the near-infrared fluorophore IRD 41. We have used various chemical treatments to prepare the tapered fiber surface for chemical, as well as physical, binding of fluorophores. We have carried out real-time hybridization tests for IRD 41-labeled oligonucleotide, at various probe concentrations, binding to complementary oligonucleotide cross-linked to the tapered fiber surface. The biospecificity of our sensor is confirmed through hybridization tests with a control oligonucleotide. Short oligonucleotides (20-mer) bound to the fiber surface have been used to detect near-IR dye-labeled complementary sequences at subnanomolar levels. Sandwich assays with Helicobacter pylori total RNA were conducted to examine the capability of the biosensor for detecting bacterial cells using rRNA as the target. The results indicate that this fluorosensor is capable of detecting H. pylori in a sandwich assay at picomolar concentrations.

Binding Sites↗

Psychological adaptation and adjustment of mothers of children with congenital heart disease: stress, coping, and family functioning.

OBJECTIVE: Investigate support for the transactional stress and coping model for mothers of children with congenital heart defects, in accounting for the variance in maternal adjustment. METHODS: Participants were 52 mothers of children recruited from a university medical center. Measures included illness variables, cognitive processes (i.e., appraisals of stress, expectations, methods of coping, family functioning, and maternal psychological adjustment). RESULTS: Maternal adjustment was associated with high levels of daily stress and palliative coping techniques and was not significantly associated with severity of the cardiac defect. Together, the variables of the model accounted for approximately 38% of the variance in maternal adjustment. CONCLUSIONS: The findings are in accord with previous research among other chronically ill populations in suggesting an association between stress, coping, and maternal adjustment. Within the limitations of the study, the data were interpreted to support the utility of theoretical models in identifying areas in need of intervention across chronic illness groups.

Adaptation, Psychological↗

Irritant contact stomatitis: a review of the condition.

Several different types of interactions are possible between a chemical, a mixture of chemicals, and associated extrinsic factors (i.e., mechanical irritation) in the oral mucosa. These interactions can be broadly classified as irritative or allergenic in nature. In each case, the pathology usually includes mucosal inflammation. The information compiled and reviewed in this article suggests that, given the broad definition of surface lesions/mucosal abnormalities, there may be a continuum of irritation that can be termed "irritant contact stomatitis." This may be due to the fact that the mouth is lined with highly vascular mucosa that turns over rapidly compared to the skin, and may or may not be covered by keratin. Some regions in the mouth are uniquely sensitive to irritants because they can penetrate through the tissue easily. Key factors involved in the potential development of irritation are: inherent irritation potential of the agent, amount of exposure (concentration, duration, and frequency), ability to penetrate the tissue, and inherent reactivity of the subject as well as other extrinsic factors. Irritation leading to oral mucosal alterations is a common occurrence caused by a wide variety of exposures and insults to the oral cavity. Various irritants such as foods, chemicals, friction, thermal/mechanical injury, metals, spices, and oral care products have been documented to cause irritant reactions in susceptible individuals, particularly if used under exaggerated exposure conditions. It is important to note that most irritation in the oral cavity tends to reverse quickly when the causative agent is removed. Oral irritation is a commonly occurring phenomenon. Thus, it is important that the clinician be aware of the clinical manifestations and etiology of the condition.

Allergens↗