Showing papers by "University of Kentucky published in 2004"

Psychological Stress and the Human Immune System: A Meta-Analytic Study of 30 Years of Inquiry

Abstract: The present report meta-analyzes more than 300 empirical articles describing a relationship between psychological stress and parameters of the immune system in human participants. Acute stressors (lasting minutes) were associated with potentially adaptive upregulation of some parameters of natural immunity and downregulation of some functions of specific immunity. Brief naturalistic stressors (such as exams) tended to suppress cellular immunity while preserving humoral immunity. Chronic stressors were associated with suppression of both cellular and humoral measures. Effects of event sequences varied according to the kind of event (trauma vs. loss). Subjective reports of stress generally did not associate with immune change. In some cases, physical vulnerability as a function of age or disease also increased vulnerability to immune change during stressors.

Assessment of mindfulness by self-report: the Kentucky inventory of mindfulness skills.

Abstract: A self-report inventory for the assessment of mindfulness skills was developed, and its psychometric characteristics and relationships with other constructs were examined. Participants included thr...

Taking Stock of Networks and Organizations: A Multilevel Perspective

Abstract: The central argument of network research is that actors are embedded in networks of interconnected social relationships that offer opportunities for and constraints on behavior. We review research on the antecedents and consequences of networks at the interpersonal, interunit, and interorganizational levels of analysis, evaluate recent theoretical and empirical trends, and give directions for future research, highlighting the importance of investigating cross-level network phenomena.

Behavioral syndromes: An integrative overview

Abstract: A behavioral syndrome is a suite of correlated behaviors expressed either within a given behavioral context (e.g., correlations between foraging behaviors in different habitats) or across different contexts (e.g., correlations among feeding, antipredator, mating, aggressive, and dispersal behaviors). For example, some individuals (and genotypes) might be generally more aggressive, more active or bold, while others are generally less aggressive, active or bold. This phenomenon has been studied in detail in humans, some primates, laboratory rodents, and some domesticated animals, but has rarely been studied in other organisms, and rarely examined from an evolutionary or ecological perspective. Here, we present an integrative overview on the potential importance of behavioral syndromes in evolution and ecology. A central idea is that behavioral correlations generate tradeoffs; for example, an aggressive genotype might do well in situations where high aggression is favored, but might be inappropriate...

The JAK/STAT signaling pathway

Abstract: The Janus kinase/signal transducers and activators of transcription (JAK/STAT) pathway is one of a handful of pleiotropic cascades used to transduce a multitude of signals for development and homeostasis in animals, from humans to flies. In mammals, the JAK/STAT pathway is the principal signaling

A classification system for seed dormancy

Abstract: The proposal is made that seed scientists need an internationally acceptable hierarchical system of classification for seed dormancy. Further, we suggest that a modified version of the scheme of the Russian seed physiologist Marianna G. Nikolaeva be adopted. The modified system includes three hierarchical layers – class, level and type; thus, a class may contain levels and types, and a level may contain only types. The system includes five classes of dormancy: physiological dormancy (PD), morphological dormancy (MD), morphophysiological dormancy (MPD), physical dormancy (PY) and combinational dormancy (PY + PD). The most extensive classification schemes are for PD, which contains three levels and five types (in the non-deep level), and MPD, which contains eight levels but no types. PY is not subdivided at all but probably should be, for reasons given. Justifications are presented for not including mechanical dormancy or chemical dormancy in the modified scheme. PD (non-deep level) is the most common kind of dormancy, and occurs in gymnosperms (Coniferales, Gnetales) and in all major clades of angiosperms. Since, first, this is the class and level of dormancy in seeds of wild populations of Arabidopsis thaliana and, secondly, Type 1 (to which seeds of A. thaliana belong) is also common, and geographically and phylogenetically widespread, it seems that biochemical, molecular and genetic studies on seed dormancy in this model species might have rather broad application in explaining the basic mechanism(s) of physiological dormancy in seeds.

Aligned multiwalled carbon nanotube membranes.

Abstract: An array of aligned carbon nanotubes (CNTs) was incorporated across a polymer film to form a well-ordered nanoporous membrane structure This membrane structure was confirmed by electron microscopy, anisotropic electrical conductivity, gas flow, and ionic transport studies The measured nitrogen permeance was consistent with the flux calculated by Knudsen diffusion through nanometer-scale tubes of the observed microstructure Data on Ru(NH3)6(3+) transport across the membrane in aqueous solution also indicated transport through aligned CNT cores of the observed microstructure The lengths of the nanotubes within the polymer film were reduced by selective electrochemical oxidation, allowing for tunable pore lengths Oxidative trimming processes resulted in carboxylate end groups that were readily functionalized at the entrance to each CNT inner core Membranes with CNT tips that were functionalized with biotin showed a reduction in Ru(NH3)6(3+) flux by a factor of 15 when bound with streptavidin, thereby demonstrating the ability to gate molecular transport through CNT cores for potential applications in chemical separations and sensing

A Correlation-Based Transition Model Using Local Variables—Part I: Model Formulation

Abstract: A new correlation-based transition model has been developed, which is based strictly on local variables. As a result, the transition model is compatible with modern computational fluid dynamics (CFD) approaches, such as unstructured grids and massive parallel execution. The model is based on two transport equations, one for intermittency and one for the transition onset criteria in terms of momentum thickness Reynolds number. The proposed transport equations do not attempt to model the physics of the transition process (unlike, e.g., turbulence models) but form a framework for the implementation of correlation-based models into general-purpose CFD methods. Part I (this part) of this paper gives a detailed description of the mathematical formulation of the model and some of the basic test cases used for model validation, including a two-dimensional turbine blade. Part II (Langtry, R. B., Menter, F. R., Likki, S. R., Suzen, Y. B., Huang, P. G., and Volker, S., 2006, ASME J. Turbomach., 128(3), pp. 423–434) of the paper details a significant number of test cases that have been used to validate the transition model for turbomachinery and aerodynamic applications. The authors believe that the current formulation is a significant step forward in engineering transition modeling, as it allows the combination of correlation-based transition models with general purpose CFD codes.

The Collaborative Cross, a community resource for the genetic analysis of complex traits

Abstract: The goal of the Complex Trait Consortium is to promote the development of resources that can be used to understand, treat and ultimately prevent pervasive human diseases. Existing and proposed mouse resources that are optimized to study the actions of isolated genetic loci on a fixed background are less effective for studying intact polygenic networks and interactions among genes, environments, pathogens and other factors. The Collaborative Cross will provide a common reference panel specifically designed for the integrative analysis of complex systems and will change the way we approach human health and disease.

Relationship of blood transfusion and clinical outcomes in patients with acute coronary syndromes.

Abstract: ContextIt is unclear if blood transfusion in anemic patients with acute coronary syndromes is associated with improved survival.ObjectiveTo determine the association between blood transfusion and mortality among patients with acute coronary syndromes who develop bleeding, anemia, or both during their hospital course.Design, Setting, and PatientsWe analyzed 24 112 enrollees in 3 large international trials of patients with acute coronary syndromes (the GUSTO IIb, PURSUIT, and PARAGON B trials). Patients were grouped according to whether they received a blood transfusion during the hospitalization. The association between transfusion and outcome was assessed using Cox proportional hazards modeling that incorporated transfusion as a time-dependent covariate and the propensity to receive blood, and a landmark analysis.Main Outcome MeasureThirty-day mortality.ResultsOf the patients included, 2401 (10.0%) underwent at least 1 blood transfusion during their hospitalization. Patients who underwent transfusion were older and had more comorbid illness at presentation and also had a significantly higher unadjusted rate of 30-day death (8.00% vs 3.08%; P<.001), myocardial infarction (MI) (25.16% vs 8.16%; P<.001), and death/MI (29.24% vs 10.02%; P<.001) compared with patients who did not undergo transfusion. Using Cox proportional hazards modeling that incorporated transfusion as a time-dependent covariate, transfusion was associated with an increased hazard for 30-day death (adjusted hazard ratio [HR], 3.94; 95% confidence interval [CI], 3.26-4.75) and 30-day death/MI (HR, 2.92; 95% CI, 2.55-3.35). In the landmark analysis that included procedures and bleeding events, transfusion was associated with a trend toward increased mortality. The predicted probability of 30-day death was higher with transfusion at nadir hematocrit values above 25%.ConclusionsBlood transfusion in the setting of acute coronary syndromes is associated with higher mortality, and this relationship persists after adjustment for other predictive factors and timing of events. Given the limitations of post hoc analysis of clinical trials data, a randomized trial of transfusion strategies is warranted to resolve the disparity in results between our study and other observational studies. We suggest caution regarding the routine use of blood transfusion to maintain arbitrary hematocrit levels in stable patients with ischemic heart disease.

Incipient Alzheimer's disease: Microarray correlation analyses reveal major transcriptional and tumor suppressor responses

Abstract: The pathogenesis of incipient Alzheimer's disease (AD) has been resistant to analysis because of the complexity of AD and the overlap of its early-stage markers with normal aging. Gene microarrays provide new tools for addressing complexity because they allow overviews of the simultaneous activity of multiple cellular pathways. However, microarray data interpretation is often hindered by low statistical power, high false positives or false negatives, and by uncertain relevance to functional endpoints. Here, we analyzed hippocampal gene expression of nine control and 22 AD subjects of varying severity on 31 separate microarrays. We then tested the correlation of each gene's expression with MiniMental Status Examination (MMSE) and neurofibrillary tangle (NFT) scores across all 31 subjects regardless of diagnosis. These well powered tests revealed a major transcriptional response comprising thousands of genes significantly correlated with AD markers. Several hundred of these genes were also correlated with AD markers across only control and incipient AD subjects (MMSE > 20). Biological process categories associated with incipient AD-correlated genes were identified statistically (ease program) and revealed up-regulation of many transcription factor/signaling genes regulating proliferation and differentiation, including tumor suppressors, oligodendrocyte growth factors, and protein kinase A modulators. In addition, up-regulation of adhesion, apoptosis, lipid metabolism, and initial inflammation processes occurred, and down-regulation of protein folding/metabolism/transport and some energy metabolism and signaling pathways took place. These findings suggest a new model of AD pathogenesis in which a genomically orchestrated up-regulation of tumor suppressor-mediated differentiation and involution processes induces the spread of pathology along myelinated axons.

Electromechanical integration of cardiomyocytes derived from human embryonic stem cells.

Abstract: Cell therapy is emerging as a promising strategy for myocardial repair. This approach is hampered, however, by the lack of sources for human cardiac tissue and by the absence of direct evidence for functional integration of donor cells into host tissues. Here we investigate whether cells derived from human embryonic stem (hES) cells can restore myocardial electromechanical properties. Cardiomyocyte cell grafts were generated from hES cells in vitro using the embryoid body differentiating system. This tissue formed structural and electromechanical connections with cultured rat cardiomyocytes. In vivo integration was shown in a large-animal model of slow heart rate. The transplanted hES cell-derived cardiomyocytes paced the hearts of swine with complete atrioventricular block, as assessed by detailed three-dimensional electrophysiological mapping and histopathological examination. These results demonstrate the potential of hES-cell cardiomyocytes to act as a rate-responsive biological pacemaker and for future myocardial regeneration strategies.

Carbon nanotube polymer composites

Abstract: The state of research into carbon nanotube/polymer–matrix composites for mechanical reinforcement is critically reviewed with emphasis on recent advances in CNT composite toughness. Particular interest is also given to interfacial bonding of carbon nanotubes to polymer matrices as it applies to stress transfer from the matrix to the CNT. Potential topics of oncoming focus are highlighted.

Symbioses of grasses with seedborne fungal endophytes

Abstract: Grasses (family Poaceae) and fungi of the family Clavicipitaceae have a long history of symbiosis ranging in a continuum from mutualisms to antagonisms. This continuum is particularly evident among symbioses involving the fungal genus Epichloe (asexual forms = Neotyphodium spp.). In the more mutualistic symbiota, the epichloe endophytes are vertically transmitted via host seeds, and in the more antagonistic symbiota they spread contagiously and suppress host seed set. The endophytes gain shelter, nutrition, and dissemination via host propagules, and can contribute an array of host fitness enhancements including protection against insect and vertebrate herbivores and root nematodes, enhancements of drought tolerance and nutrient status, and improved growth particularly of the root. In some systems, such as the tall fescue N. coenophialum symbioses, the plant may depend on the endophyte under many natural conditions. Recent advances in endophyte molecular biology promise to shed light on the mechanisms of the symbioses and host benefits.

Nanoparticle Surface Charges Alter Blood–Brain Barrier Integrity and Permeability

Abstract: Purpose: The blood–brain barrier (BBB) presents both a physical and electrostatic barrier to limit brain permeation of therapeutics. Previous work has demonstrated that nanoparticles (NPs) overcome the physical barrier, but there is little known regarding the effect of NP surface charge on BBB function. Therefore, this work evaluated: (1) effect of neutral, anionic and cationic charged NPs on BBB integrity and (2) NP brain permeability.Methods: Emulsifying wax NPs were prepared from warm oil-in-water microemulsion precursors using neutral, anionic or cationic surfactants to provide the corresponding NP surface charge. NPs were characterized by particle size and zeta potential. BBB integrity and NP brain permeability were evaluated by in situ rat brain perfusion.Results: Neutral NPs and low concentrations of anionic NPs were found to have no effect on BBB integrity, whereas, high concentrations of anionic NPs and cationic NPs disrupted the BBB. The brain uptake rates of anionic NPs at lower concentrations ...

Identification of humans using gait

Abstract: We propose a view-based approach to recognize humans from their gait. Two different image features have been considered: the width of the outer contour of the binarized silhouette of the walking person and the entire binary silhouette itself. To obtain the observation vector from the image features, we employ two different methods. In the first method, referred to as the indirect approach, the high-dimensional image feature is transformed to a lower dimensional space by generating what we call the frame to exemplar (FED) distance. The FED vector captures both structural and dynamic traits of each individual. For compact and effective gait representation and recognition, the gait information in the FED vector sequences is captured in a hidden Markov model (HMM). In the second method, referred to as the direct approach, we work with the feature vector directly (as opposed to computing the FED) and train an HMM. We estimate the HMM parameters (specifically the observation probability B) based on the distance between the exemplars and the image features. In this way, we avoid learning high-dimensional probability density functions. The statistical nature of the HMM lends overall robustness to representation and recognition. The performance of the methods is illustrated using several databases.

Thermal and Flammability Properties of Polypropylene/Carbon Nanotube Nanocomposites

Abstract: The thermal and flammability properties of polypropylene/multi-walled carbon nanotube, (PP/MWNT) nanocomposites were measured with the MWNT content varied from 0.5 to 4% by mass. Dispersion of MWNTs in these nanocomposites was characterized by SEM and optical microscopy. Flammability properties were measured with a cone calorimeter in air and a gasification device in a nitrogen atmosphere. A significant reduction in the peak heat release rate was observed; the greatest reduction was obtained with a MWNT content of 1% by mass. Since the addition of carbon black powder to PP did not reduce the heat release rate as much as with the PP/MWNT nanocomposites, the size and shape of carbon particles appear to be important for effectively reducing the flammability of PP. The radiative ignition delay time of a nanocomposite having less than 2% by mass of MWNT was shorter than that of PP due to an increase in the radiation in-depth absorption coefficient by the addition of carbon nanotubes. The effects of residual iron particles and of defects in the MWNTs on the heat release rate of the nanocomposite were not significant. The flame retardant performance was achieved through the formation of a relatively uniform network-structured floccule layer covering the entire sample surface without any cracks or gaps. This layer re-emitted much of the incident radiation back into the gas phase from its hot surface and thus reduced the transmitted flux to the receding PP layers below it, slowing the PP pyrolysis rate. To gain insight into this phenomena, thermal conductivities of the nanocomposites were measured as a function of temperature while the thermal conductivity of the nanocomposite increases with an increase in MWNT content, the effect being particularly large above 160 °C, this increase is not as dramatic as the increase in electrical conductivity, however.

Transcriptome of Arabidopsis leaf senescence

Abstract: Leaf senescence is a complex developmental process during which essential nutrients are recycled. In order to unravel the biochemical pathways and regulatory mechanisms that underlie this process, it would be valuable to examine the transcriptome associated with leaf senescence. Accordingly, an Arabidopsis thaliana leaf senescence cDNA library with approximately 104 recombinant clones was subjected to large-scale single-pass sequencing. Approximately 6200 expressed sequence tags (ESTs) were obtained, corresponding to 2491 unique genes. These included 134 genes encoding transcription factors and 182 genes whose products are components of signal transduction pathways, such as the mitogen-activated protein kinase (MAPK) cascades. A total of 116 of these genes are predicted to be involved in protein turnover, including 75 genes associated with the ubiquitin–proteasome pathway and 35 proteinases. Many of the genes are predicted to encode transporters for ions, amino acids and sugars, consistent with the substantial nutrient recycling during leaf senescence. In addition, this study revealed ESTs for 98 annotated genes for which ESTs did not previously exist and 46 novel transcribed units that have not previously been annotated in the Arabidopsis genome. Approximately one-third of the 2491 genes are predicted to encode proteins with unknown functions. The genes are distributed evenly on the five chromosomes.

What Is an Intracluster Correlation Coefficient? Crucial Concepts for Primary Care Researchers

Abstract: BACKGROUND Primary care research often involves clustered samples in which subjects are randomized at a group level but analyzed at an individual level. Analyses that do not take this clustering into account may report significance where none exists. This article explores the causes, consequences, and implications of cluster data. METHODS Using a case study with accompanying equations, we show that clustered samples are not as statistically efficient as simple random samples. RESULTS Similarity among subjects within preexisting groups or clusters reduces the variability of responses in a clustered sample, which erodes the power to detect true differences between study arms. This similarity is expressed by the intracluster correlation coefficient, or ρ (rho), which compares the within-group variance with the between-group variance. Rho is used in equations along with the cluster size and the number of clusters to calculate the effective sample size (ESS) in a clustered design. The ESS should be used to calculate power in the design phase of a clustered study. Appropriate accounting for similarities among subjects in a cluster almost always results in a net loss of power, requiring increased total subject recruitment. Increasing the number of clusters enhances power more efficiently than does increasing the number of subjects within a cluster. CONCLUSIONS Primary care research frequently uses clustered designs, whether consciously or unconsciously. Researchers must recognize and understand the implications of clusters to avoid costly sample size errors.

The C. elegans microRNA let-7 binds to imperfect let-7 complementary sites from the lin-41 3′UTR

Abstract: Caenorhabditis elegans let-7, a founding member of the microRNA family, is predicted to bind to six sites in the 3′UTR of the mRNA of its target gene, lin-41, to down-regulate LIN-41. Here, we demonstrate that wild-type let-7 microRNA binds in vitro to RNA from the lin-41 3′UTR. This interaction is dependent on two conserved let-7 complementary sites (LCSs). A 27-nucleotide sequence between the LCSs is also necessary for down-regulation in vivo. LCS mutations compensatory to the lesion in let-7(n2853) can partially restore lin-41 3′UTR function in a let-7(n2853) background, providing the first experimental evidence for an animal miRNA binding directly to its validated target in vivo.

Mouse Models of Abdominal Aortic Aneurysms

Abstract: Many mouse models of abdominal aortic aneurysms have been developed that use a diverse array of methods for producing the disease, including genetic manipulation and chemical induction. These models could provide insight into potential mechanisms in the development of this disease. Although experimental studies on abdominal aortic aneurysms (AAAs) have used a variety of mammalian and avian approaches, there is an increasing reliance on the use of mice. The models recapitulate some facets of the human disease including medial degeneration, inflammation, thrombus formation, and rupture. Most of the mouse models of AAA are evoked either by genetically defined approaches or by chemical means. The genetic approaches are spontaneous and engineered mutations. These include defects in extracellular matrix maturation, increased degradation of elastin and collagen, aberrant cholesterol homeostasis, and enhanced production of angiotensin peptides. The chemical approaches include the intraluminal infusion of elastase, periaortic incubations of calcium chloride, and subcutaneous infusion of AngII. A common feature of these models is the reduction of AAA incidence and severity by the prophylactic administration of matrix metalloproteinase (MMP) inhibitors or genetically engineered deficiencies of specific members of this proteolytic protein family. The validation of mouse models of AAAs will provide insight into the mechanisms of progression of the human disease.

Flow-induced properties of nanotube-filled polymer materials.

Abstract: Carbon nanotubes (CNTs) are under intense investigation in materials science owing to their potential for modifying the electrical conductivity σ, shear viscosity η, and other transport properties of polymeric materials. These particles are hybrids of filler and nanoscale additives because their lengths are macroscopic whereas their cross-sectional dimensions are closer to molecular scales. The combination of extended shape, rigidity and deformability allows CNTs to be mechanically dispersed in polymer matrices in the form of disordered 'jammed' network structures. Our measurements on representative network-forming multiwall nanotube (MWNT) dispersions in polypropylene indicate that these materials exhibit extraordinary flow-induced property changes. Specifically, σ and η both decrease strongly with increasing shear rate, and these nanocomposites exhibit impressively large and negative normal stress differences, a rarely reported phenomenon in soft condensed matter. We illustrate the practical implications of these nonlinear transport properties by showing that MWNTs eliminate die swell in our nanocomposites, an effect crucial for their processing.

Measuring Alliances: the Correlates of War Formal Interstate Alliance Dataset, 1816–2000

Abstract: This article serves as a companion to the release of Version 3.0 of the Correlates of War Formal Interstate Alliance Dataset, 1816–2000. First released in 1966, the Correlates of War alliance data have greatly influenced quantitative studies of conflict, providing an important variable in the study of international conflict and cooperation. The article begins by describing the historical development and the major characteristics of the alliance dataset. The second section then discusses the procedures used to both identify and code each alliance in this revised and extended version of the data, and this is followed by a description of several important changes made to the original coding rules in order to develop this dataset, with the most notable of these changes being a more determined reliance on treaty texts rather than historical accounts for identification of alliances and alliance types. To show the effects of the revised coding decisions and the enlarged temporal domain, the final section of the ...