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Search Results: 1 - 10 of 329254 matches for " Michelle S. Jansen "
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Expression of mammalian GPCRs in C. elegans generates novel behavioural responses to human ligands
Michelle S Teng, Martijn PJ Dekkers, Bee Ng, Suzanne Rademakers, Gert Jansen, Andrew G Fraser, John McCafferty
BMC Biology , 2006, DOI: 10.1186/1741-7007-4-22
Abstract: Expression of Sstr2 and CCR5 in gustatory neurons allow C. elegans to specifically detect and respond to somatostatin and MIP-1α respectively in a robust avoidance assay. We demonstrate that mammalian heterologous GPCRs can signal via different endogenous Gα subunits in C. elegans, depending on which cells it is expressed in. Furthermore, pre-exposure of GPCR transgenic animals to its ligand leads to receptor desensitisation and behavioural adaptation to subsequent ligand exposure, providing further evidence of integration of the mammalian GPCRs into the C. elegans sensory signalling machinery. In structure-function studies using a panel of somatostatin-14 analogues, we identified key residues involved in the interaction of somatostatin-14 with Sstr2.Our results illustrate a remarkable evolutionary plasticity in interactions between mammalian GPCRs and C. elegans signalling machinery, spanning 800 million years of evolution. This in vivo system, which imparts novel avoidance behaviour on C. elegans, thus provides a simple means of studying and screening interaction of GPCRs with extracellular agonists, antagonists and intracellular binding partners.The nematode C. elegans represents a simple and experimentally tractable multicellular organism, which has been used to investigate many biological processes, including chemosensory behaviour [1]. It uses only 11 pairs of amphid chemosensory neurons to detect environmental signals. As in mammalian systems, GPCRs play an important role in the detection of sensory signals, and these signals are relayed in the cell by heterotrimeric G proteins. In contrast to mammalian chemosensory systems, the C. elegans sensory neurons express multiple GPCRs in each sensory neuron using several Gα subunits per neuron for sensory transduction, thus allowing the nematode to respond specifically to different environmental cues using only a few sensory neurons [2-4].Current methods utilised to study mammalian GPCR-ligand interactions are mostl
Improved Bone Morphogenetic Protein-2 Retention in an Injectable Collagen Matrix Using Bifunctional Peptides
Paul T. Hamilton, Michelle S. Jansen, Sathya Ganesan, R. Edward Benson, Robin Hyde-DeRuyscher, Wayne F. Beyer, Joseph C. Gile, Shrikumar A. Nair, Jonathan A. Hodges, Hanne Gr?n
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0070715
Abstract: To promote healing of many orthopedic injuries, tissue engineering approaches are being developed that combine growth factors such as Bone Morphogenetic Proteins (BMP) with biomaterial carriers. Although these technologies have shown great promise, they still face limitations. We describe a generalized approach to create target-specific modular peptides that bind growth factors to implantable biomaterials. These bifunctional peptide coatings provide a novel way to modulate biology on the surface of an implant. Using phage display techniques, we have identified peptides that bind with high affinity to BMP-2. The peptides that bind to BMP-2 fall into two different sequence clusters. The first cluster of peptide sequences contains the motif W-X-X-F-X-X-L (where X can be any amino acid) and the second cluster contains the motif F-P-L-K-G. We have synthesized bifunctional peptide linkers that contain BMP-2 and collagen-binding domains. Using a rat ectopic bone formation model, we have injected rhBMP-2 into a collagen matrix with or without a bifunctional BMP-2: collagen peptide (BC-1). The presence of BC-1 significantly increased osteogenic cellular activity, the area of bone formed, and bone maturity at the site of injection. Our results suggest that bifunctional peptides that can simultaneously bind to a growth factor and an implantable biomaterial can be used to control the delivery and release of growth factors at the site of implantation.
On the separation of timescales in spring-block earthquake models
S. Hergarten ,F. Jansen
Nonlinear Processes in Geophysics (NPG) , 2005,
Abstract: One of the most widespread spring-block earthquake models, the Olami-Feder-Christensen model, is investigated without making the assumption that the duration of individual earthquakes is negligible. While the Gutenberg-Richter law for the size distribution of earthquakes is preserved qualitatively for earthquakes of finite duration, the b-value decreases with increasing earthquake duration. The effect decreases with increasing lattice size, although it is not clear whether it completely vanishes in the limit of infinite grid size. For realistic values of earthquake duration, the effect is negligible, so that the original model with zero earthquake duration is appropriate for most applications.
The Association of Night Shift Work with the Development of Breast Cancer in Women  [PDF]
P. I. J. Moukangoe, M. S. Jansen van Rensburg
Open Journal of Epidemiology (OJEpi) , 2015, DOI: 10.4236/ojepi.2015.51003
Abstract: Breast cancer is a serious public health concern in South Africa and globally. It is estimated that one in seven South Africans will develop cancer in their lifetime. According to a case-controlled study, 80% of cancer cases are thought to be due to external, non-inherited factors, which could potentially have been prevented. The objectives of the current case-control study were: 1) to determine the relationship between night shift work and the development of breast cancer; 2) to explore the relationship between night shift work and other types of cancer; 3) to explore any difference between night shift work and breast cancer, and night shift work and other types of cancer. A total of 106 research participants were selected using non-probability, convenience sampling methods and interviewed using a structured questionnaire. Seventy-two (68%) of the women who were interviewed were black, while 32% (n = 35) were white. Of the 106 research participants, 82% (n = 87) had a history of being employed, while 18% (n = 19) had never been employed. Analysed data showed that 29% (n = 31) of the women had a history of working night shift. Of the 31 research participants who reported having worked night shift, 90% (n = 28) had actually done rotating shift work, rather than regular night shift work. The odds ratio of working night shift was found to be 1.24 (OR = 1.24, p = 0.615) higher in breast cancer research participants compared to research participants diagnosed with other types of cancer—odds ratio of 0.80 (p = 0.610). For rotational work, the OR was 1.445, indicating a higher risk than for shift work. It is recommended that the relationship between working night shift and breast cancer risk be explored further through cross-sectional and cohort studies.
The aims of initiation ceremonies at universities: Comparisons in time and space1
N. S. Jansen van Rensburg
Koers : Bulletin for Christian Scholarship , 1990, DOI: 10.4102/koers.v55i1-4.1013
Abstract: In this article initiation practices at South African universities are analysed and compared with initiation ceremonies described in anthropological literature. It is argued that any initiation ceremony has at least the partial aim of preparing initiates for the roles and functions in society or specific organizations. Naturally a reasonable degree of harmony between the intent of initiation on the one hand and the values of an institution on the other hand can be expected. The intention of initiation usually is to prepare one for a position or rote by means of the expression of certain values. On the question whether this harmony between ideas and actions is found in the case of existent initiation ceremonies at South African universities, the answer is negative. These ceremonies do not aim to convey and develop attitudes and values essential to a university and in fact do not prepare first-year students for their new environment and a community of scholars. The way in which universities transcend their authority by condoning and officially allowing the demeaning initiation practices is also questioned.
Anthropology, social change and the reconstruction of South African society1
N. S. Jansen van Rensburg
Koers : Bulletin for Christian Scholarship , 1994, DOI: 10.4102/koers.v59i1.653
Abstract: In this article it is argued that, since the abuse of anthropology in the colonial and apartheid eras, the responsive relationship between anthropology and society has been re-emphasised. In the reconstruction of South African society, therefore, anthropologists will not be allowed the luxury of evading their social responsibility. In their re-invention of anthropology as a humane science, and the reiteration of their commitment to accountability and relevance, these scientists ought to build their discipline upon the investigation of the major consequences of differential power and inequality. This could be helpful in creating new forms of co-existence in South Africa
Berman-Konsowa principle for reversible Markov jump processes
F. den Hollander,S. Jansen
Mathematics , 2013,
Abstract: In this paper we prove a version of the Berman-Konsowa principle for reversible Markov jump processes on Polish spaces. The Berman-Konsowa principle provides a variational formula for the capacity of a pair of disjoint measurable sets. There are two versions, one involving a class of probability measures for random finite paths from one set to the other, the other involving a class of finite unit flows from one set to the other. The Berman-Konsowa principle complements the Dirichlet principle and the Thomson principle, and turns out to be especially useful for obtaining sharp estimates on crossover times in metastable interacting particle systems.
Ideal mixture approximation of cluster size distributions at low density
S. Jansen,W. K?nig
Statistics , 2011, DOI: 10.1007/s10955-012-0499-5
Abstract: We consider an interacting particle system in continuous configuration space. The pair interaction has an attractive part. We show that, at low density, the system behaves approximately like an ideal mixture of clusters (droplets): we prove rigorous bounds (a) for the constrained free energy associated with a given cluster size distribution, considered as an order parameter, (b) for the free energy, obtained by minimising over the order parameter, and (c) for the minimising cluster size distributions. It is known that, under suitable assumptions, the ideal mixture has a transition from a gas phase to a condensed phase as the density is varied; our bounds hold both in the gas phase and in the coexistence region of the ideal mixture. The present paper improves our earlier results by taking into account the mixing entropy.
β-Defensin-2 Protein Is a Serum Biomarker for Disease Activity in Psoriasis and Reaches Biologically Relevant Concentrations in Lesional Skin
Patrick A. M. Jansen, Diana Rodijk-Olthuis, Edward J. Hollox, Marijke Kamsteeg, Geuranne S. Tjabringa, Gys J. de Jongh, Ivonne M. J. J. van Vlijmen-Willems, Judith G. M. Bergboer, Michelle M. van Rossum, Elke M. G. J. de Jong, Martin den Heijer, Andrea W. M. Evers, Mieke Bergers, John A. L. Armour, Patrick L. J. M. Zeeuwen, Joost Schalkwijk
PLOS ONE , 2009, DOI: 10.1371/journal.pone.0004725
Abstract: Background Previous studies have extensively documented antimicrobial and chemotactic activities of beta-defensins. Human beta-defensin-2 (hBD-2) is strongly expressed in lesional psoriatic epidermis, and recently we have shown that high beta-defensin genomic copy number is associated with psoriasis susceptibility. It is not known, however, if biologically and pathophysiologically relevant concentrations of hBD-2 protein are present in vivo, which could support an antimicrobial and proinflammatory role of beta-defensins in lesional psoriatic epidermis. Methodology/Principal Findings We found that systemic levels of hBD-2 showed a weak but significant correlation with beta defensin copy number in healthy controls but not in psoriasis patients with active disease. In psoriasis patients but not in atopic dermatitis patients, we found high systemic hBD-2 levels that strongly correlated with disease activity as assessed by the PASI score. Our findings suggest that systemic levels in psoriasis are largely determined by secretion from involved skin and not by genomic copy number. Modelling of the in vivo epidermal hBD-2 concentration based on the secretion rate in a reconstructed skin model for psoriatic epidermis provides evidence that epidermal hBD-2 levels in vivo are probably well above the concentrations required for in vitro antimicrobial and chemokine-like effects. Conclusions/Significance Serum hBD-2 appears to be a useful surrogate marker for disease activity in psoriasis. The discrepancy between hBD-2 levels in psoriasis and atopic dermatitis could explain the well known differences in infection rate between these two diseases.
Haemodynamic Monitoring Using Echocardiography in the Critically Ill: A Review
Michelle S. Chew
Cardiology Research and Practice , 2012, DOI: 10.1155/2012/139537
Abstract: Physicians caring for the critically ill are now expected to acquire competence in echocardiography. It has become an indispensable diagnostic and monitoring tool in acute care settings where it is generally accepted to have therapeutic impact. There are a number of indications for a critical care echocardiographic study, and the most important queries include those pertaining left and right ventricular function and filling status. Focused examinations are increasing in popularity and provide a means for systematic study, and can be easily learned and practiced by novices. This paper addresses the indications, therapeutic impact, and some of the most common questions that can be answered using echocardiography the in critically ill patient. 1. Introduction Echocardiography is now considered an indispensable tool for diagnosis and haemodynamic monitoring in critically ill patients. Indications for performing echocardiography in the ICU have expanded and it is now considered a requirement for critical care physicians to acquire competence in this mode of monitoring. Reflecting this are the numerous competency guidelines published in recent years [1–4]. Potential advantages and disadvantages of echocardiography compared to invasive haemodynamic monitoring (e.g., pulmonary artery catheter and arterial waveform analysis) in the critically ill are listed in Table 1. Table 1: Potential advantages and disadvantages of echocardiography versus invasive monitoring. This paper is not intended to be a comprehensive review of echocardiographic techniques. It does not include a review of left ventricular diastolic function, or lung ultrasound, a rapidly growing and increasingly important imaging modality [5]. Instead it addresses the indications, therapeutic impact, and some of the most common questions that can be answered using echocardiography in critically ill patients. 2. Therapeutic Impact There are no randomized trials/metaanalyses regarding the impact of echocardiography on critically ill patients. A number of studies attest to the usefulness of echocardiography in the intensive care unit [6–9]. For example in Vignon et al., TTE and TEE led to therapeutic changes in approximately 25% of critically ill, mechanically ventilated patients [6], a finding supported by later studies [8, 9]. There are a number of societal guidelines with evidence-based recommendations for the use of echocardiography in a variety of clinical situations, including intraoperative settings and in critically ill patients [10]. The best evidence for the therapeutic impact of
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