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Search Results: 1 - 10 of 229375 matches for " Jeffrey R. Martens "
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Ordered Assembly of the Adhesive and Electrochemical Connections within Newly Formed Intercalated Disks in Primary Cultures of Adult Rat Cardiomyocytes
Sarah B. Geisler,Kathleen J. Green,Lori L. Isom,Sasha Meshinchi,Jeffrey R. Martens,Mario Delmar,Mark W. Russell
Journal of Biomedicine and Biotechnology , 2010, DOI: 10.1155/2010/624719
Abstract: The intercalated disk (ID) is a complex structure that electromechanically couples adjoining cardiac myocytes into a functional syncitium. The integrity of the disk is essential for normal cardiac function, but how the diverse elements are assembled into a fully integrated structure is not well understood. In this study, we examined the assembly of new IDs in primary cultures of adult rat cardiac myocytes. From 2 to 5 days after dissociation, the cells flatten and spread, establishing new cell-cell contacts in a manner that recapitulates the in vivo processes that occur during heart development and myocardial remodeling. As cells make contact with their neighbors, transmembrane adhesion proteins localize along the line of apposition, concentrating at the sites of membrane attachment of the terminal sarcomeres. Cx43 gap junctions and ankyrin-G, an essential cytoskeletal component of voltage gated sodium channel complexes, were secondarily recruited to membrane domains involved in cell-cell contacts. The consistent order of the assembly process suggests that there are specific scaffolding requirements for integration of the mechanical and electrochemical elements of the disk. Defining the relationships that are the foundation of disk assembly has important implications for understanding the mechanical dysfunction and cardiac arrhythmias that accompany alterations of ID architecture.
Effects of Diet on Resource Utilization by a Model Human Gut Microbiota Containing Bacteroides cellulosilyticus WH2, a Symbiont with an Extensive Glycobiome
Nathan P. McNulty,Meng Wu,Alison R. Erickson,Chongle Pan,Brian K. Erickson,Eric C. Martens,Nicholas A. Pudlo,Brian D. Muegge,Bernard Henrissat,Robert L. Hettich,Jeffrey I. Gordon
PLOS Biology , 2013, DOI: 10.1371/journal.pbio.1001637
Abstract: The human gut microbiota is an important metabolic organ, yet little is known about how its individual species interact, establish dominant positions, and respond to changes in environmental factors such as diet. In this study, gnotobiotic mice were colonized with an artificial microbiota comprising 12 sequenced human gut bacterial species and fed oscillating diets of disparate composition. Rapid, reproducible, and reversible changes in the structure of this assemblage were observed. Time-series microbial RNA-Seq analyses revealed staggered functional responses to diet shifts throughout the assemblage that were heavily focused on carbohydrate and amino acid metabolism. High-resolution shotgun metaproteomics confirmed many of these responses at a protein level. One member, Bacteroides cellulosilyticus WH2, proved exceptionally fit regardless of diet. Its genome encoded more carbohydrate active enzymes than any previously sequenced member of the Bacteroidetes. Transcriptional profiling indicated that B. cellulosilyticus WH2 is an adaptive forager that tailors its versatile carbohydrate utilization strategy to available dietary polysaccharides, with a strong emphasis on plant-derived xylans abundant in dietary staples like cereal grains. Two highly expressed, diet-specific polysaccharide utilization loci (PULs) in B. cellulosilyticus WH2 were identified, one with characteristics of xylan utilization systems. Introduction of a B. cellulosilyticus WH2 library comprising >90,000 isogenic transposon mutants into gnotobiotic mice, along with the other artificial community members, confirmed that these loci represent critical diet-specific fitness determinants. Carbohydrates that trigger dramatic increases in expression of these two loci and many of the organism's 111 other predicted PULs were identified by RNA-Seq during in vitro growth on 31 distinct carbohydrate substrates, allowing us to better interpret in vivo RNA-Seq and proteomics data. These results offer insight into how gut microbes adapt to dietary perturbations at both a community level and from the perspective of a well-adapted symbiont with exceptional saccharolytic capabilities, and illustrate the value of artificial communities.
Ethical and Regulatory Issues with Residual Newborn Screening Dried Bloodspots  [PDF]
Erin Rothwell, Jeffrey R. Botkin
Open Journal of Preventive Medicine (OJPM) , 2015, DOI: 10.4236/ojpm.2015.510045
Abstract: After newborn screening is completed, most states retain leftover dried bloodspots. These dried bloodspots are stored for varying lengths of time among different state newborn screening programs. Dried bloodspots are a unique and valuable resource for the development of new newborn screening tests, quality assurance and biomedical research. Recent changes to the 2014 Newborn Screening Reauthorization Saves Lives Act require explicit parental consent for the retention and use of dried bloodspots in federally funded research. This has raised several ethical and regulatory issues and highlighted the challenges of respecting individual autonomy and public health goals. This article provides an overview of these issues and discusses methods for obtaining parental consent. These issues may be applicable to consent for the storage and use of biospecimens among other settings according to proposed changes to the Common Rule.
Peripheral Vascular Dysfunction in Chronic Kidney Disease
Christopher R. Martens,David G. Edwards
Cardiology Research and Practice , 2011, DOI: 10.4061/2011/267257
Abstract: There is an increased prevalence of cardiovascular disease- (CVD-) related mortality in patients with chronic kidney disease (CKD). Endothelial dysfunction is a primary event in the development of atherosclerosis and hypertension and likely contributes to the elevated cardiovascular risk in CKD. Endothelial dysfunction has been shown to occur in the peripheral vasculature of patients with both severe and moderate CKD. Mechanisms include oxidative stress, L-arginine deficiency, and elevated plasma levels of ADMA. Interventions designed to restore vascular function in patients with CKD have shown mixed results. Evidence from cell culture studies suggest that the accumulation of uremic toxins inhibits L-arginine transport and reduces nitric oxide production. The results of these studies suggest that endothelial dysfunction may become less reversible with advancing kidney disease. The purpose of this paper is to present the current literature pertaining to potential mechanisms of peripheral vascular dysfunction in chronic kidney disease and to identify possible targets for treatment. 1. Introduction Chronic kidney disease (CKD) is a major public health concern affecting nearly 20 million people in the United States alone [1]. Patients with CKD are at greater risk of cardiovascular disease- (CVD-) related morbidity and mortality than individuals without CKD with similar cardiovascular risk factors and tend to die before reaching end-stage renal disease (ESRD) [2–5]. Treatments aimed solely at reducing traditional cardiovascular risk factors do not improve cardiovascular function in patients with late-stage CKD [6]. Therefore, traditional CVD risk factors alone cannot explain the high incidence of CVD in CKD. Endothelial dysfunction is a precursor to the development of atherosclerosis [7, 8] and has been shown to be associated with increased cardiovascular risk in patients with left ventricular dysfunction and congestive heart failure [9–11]. The combination of traditional risk factors in CKD is not enough to explain the high incidence of CVD and endothelial dysfunction has been suggested to play a role in the increased CV risk in CKD [12, 13]. In support of this, a longitudinal study of patients with end-stage renal disease (ESRD) found all cause mortality to be independently associated with impaired endothelial function [14]. The majority of studies of endothelial function in renal disease have focused on ESRD and patients receiving dialysis; however, little is known about endothelial function in earlier stages of CKD. Guidelines from the Kidney Disease
Douching: A Risk to Women's Healthcare?
Mark Martens,Gilles R. G. Monif
Infectious Diseases in Obstetrics and Gynecology , 2003, DOI: 10.1080/10647440300025511
Width of reaction zones in A + B -> C type reaction-diffusion processes: Effects of an electric current
Kirsten Martens,Michel Droz,Zoltan Rácz
Physics , 2009, DOI: 10.1063/1.3148888
Abstract: We investigate the effects of an electric current on the width of a stationary reaction zone in an irreversible A^- + B^+ -> C reaction-diffusion process. The ion dynamics of the electrolytes A = (A^+, A^-) and B = (B^+, B^-) is described by reaction-diffusion equations obeying local electroneutrality, and the stationary state is obtained by employing reservoirs of fixed electrolyte concentrations at the opposite ends of a finite domain. We find that the width of the reaction zone decreases when the current drives the reacting ions towards the reaction zone while it increases in the opposite case. The linear response of the width to the current is estimated by developing a phenomenological theory based on conservation laws, and on electroneutrality. The theory is found to reproduce numerical solutions to a good accuracy.
Female Agassiz’s desert tortoise activity at a wind energy facility in southern California: The influence of an El Niño event  [PDF]
Josh R. Ennen, Kathie Meyer, Jeffrey Lovich
Natural Science (NS) , 2012, DOI: 10.4236/ns.2012.41006
Abstract: We compared spring-summer activity of adult female Agassiz’s Desert Tortoises (Gopherus agassizii) among three consecutive years (1997, 1998, and 1999) that differed dramatically in winter rainfall and annual plant production at a wind energy facility in the Sonoran Desert of southern California. Winter rainfall was approximately 71%, 190%, and 17% of the long-term average (October-March = 114 mm) for this area in water years (WY) 1997, 1998, and 1999, respectively. The substantial precipitation caused by an El Ni?o Southern Oscillation (ENSO) event in WY 1998 produced a generous annual food plant supply (138.2 g dry biomass/ m2) in the spring. Primary production of winter annuals during below average rainfall years (WY 1997 and WY 1999) was reduced to 98.3 and 0.2 g/m2, respectively. Mean rates of movement and mean body condition indices (mass/length) did not differ significantly among the years. The drought year following ENSO (WY 1999) was statistically similar to ENSO in every other measured value, while WY 1997 (end of a two year drought) was statistically different from ENSO using activity area, minimum number of burrows used, and percentage of non-movements. Our data suggest that female G. agassizii activity can be influenced by environmental conditions in previous years.
Rationalizing Inconsistent Definitions of Commodification: A Social Exchange Perspective  [PDF]
Jeffrey R. Oliver, Lindon J. Robison
Modern Economy (ME) , 2017, DOI: 10.4236/me.2017.811088
Abstract: Commodification is a widely used and inconsistently defined concept. Inconsistent definitions of commodification, this paper observes, exist because alternative outcomes and consequences of converting relational goods into commodities are confused with the definition of commodification-social exchanges that convert relational goods into commodities. Distinguishing between alternative outcomes and consequences of commodification and the definition of commodification allows us to rationalize inconsistent definitions of commodification. In rationalizing inconsistent definitions of commodification, it is important to distinguish between commodities (goods valued for their ability to satisfy physical needs) and relational goods (goods valued at least in part for their connections to people which enables them to satisfy socio-emotional needs). The process of commodification is described as relocating relational goods from the humanistic sphere and relocating them in the commodity sphere.
The genotype-phenotype relationship in multicellular pattern-generating models - the neglected role of pattern descriptors
Harald Martens, Siren R Veflingstad, Erik Plahte, Magni Martens, Dominique Bertrand, Stig W Omholt
BMC Systems Biology , 2009, DOI: 10.1186/1752-0509-3-87
Abstract: By combining computer simulations according to a succession of statistical experimental designs, computer graphics, automatic image analysis, human sensory descriptive analysis and multivariate data modelling, we derive a pattern descriptor model of those macroscopic, emergent aspects of the patterns that we consider of interest. The pattern descriptor model relates the values of the new, dedicated pattern descriptors to the parameter values of the original model, for example by predicting the parameter values leading to particular patterns, and provides insights that would have been hard to obtain by traditional methods.The results suggest that our approach may qualify as a general procedure for how to discover and relate relevant features and characteristics of emergent patterns to the functional relationships, parameter values and initial values of an underlying pattern-generating mathematical model.The whole development process of higher organisms can be mathematically conceptualised as a recursive mapping - i.e. successive cell differentiations leading to a sequence of unfolding patterns at many different spatiotemporal scales, each pattern defining the context for further differentiation and thus for subsequent patterning processes. A deep understanding of what causes the phenotypic variation arising from such patterning processes cannot be claimed before we are able to recreate this variation theoretically by what we call causally cohesive genotype-phenotype models (cGP models) [1]. Unlike the broader class of mechanistic mathematical models describing how complex biological phenotypes arise from the interactions of lower-level systemic entities, cGP models are distinguished by linking together (cohering) the individual's genotype and its phenotype in a causal mathematical structure. cGP models thus allow the construction of genotype-phenotype maps, i.e. mappings predicting the phenotype associated with a given genotype based on what we know about the regulat
Patient Preferences in the Treatment of Vaginal Candidiasis  [PDF]
Mark G. Martens
Open Journal of Obstetrics and Gynecology (OJOG) , 2018, DOI: 10.4236/ojog.2018.812116
Abstract: Vulvovaginal candidiasis (VVC) is one of the most frequent problems facing women and their healthcare professionals (HCP). It is difficult for providers to understand the prevalence of VVC because effective over the counter treatments (OTC), are available. It is expected that there are a great many more episodes of VVC in our patient population, as the frequency of self-treatment, success and satisfaction for those that use OTC products prior to seeing a women’s health care provider is unknown. In this study; healthcare providers were given OTC miconazole/tioconazole units for free distribution to patients for whom they diagnosed VVC by exam in their offices. Surveys for both HCP and patients were also distributed to determine the initial or recurrent nature of their symptoms and their satisfaction with their treatments. 1265 OBGYNs and 1821 NP/CNM/PAs reported on over 19,000 patients receiving a single complete treatment. Among HCPs, treatment efficacy was the primary reason for recommending miconazole/tioconazole. However, rapid onset of symptom relief, safety vs. fluconazole, patient preference for the less messy ovule, avoidance with drugs metabolized by the liver, and resistance to, or failure on, fluconazole were additional reasons noted for topical preference. Overall, patient satisfaction (n =
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