Electrical properties of breast cancer cells from impedance measurement of cell suspensions

Impedance spectroscopy of biological cells has been used to monitor cell status, e.g. cell proliferation, viability, etc. It is also a fundamental method for the study of the electrical properties of cells which has been utilised for cell identification in investigations of cell behaviour in the presence of an applied electric field, e.g. electroporation. There are two standard methods for impedance measurement on cells. The use of microelectrodes for single cell impedance measurement is one method to realise the measurement, but the variations between individual cells introduce significant measurement errors. Another method to measure electrical properties is by the measurement of cell suspensions, i.e. a group of cells within a culture medium or buffer. This paper presents an investigation of the impedance of normal and cancerous breast cells in suspension using the Maxwell-Wagner mixture theory to analyse the results and extract the electrical parameters of a single cell. The results show that normal and different stages of cancer breast cells can be distinguished by the conductivity presented by each cell. © 2010 IOP Publishing Ltd

First documentation of malaria parasites (genus Plasmodium) in the Saltmarsh Sparrow (Ammodramus caudacutus) and patterns of infection with mercury exposure

Avian malaria parasites, protist parasites of the genus Plasmodium, are extremely common in birds worldwide and have the ability to dramatically impact sensitive populations and species. Mercury, a heavy metal that accumulates in the tissues of birds, is a common environmental pollutant that may reduce immune system function and increase susceptibility to malaria parasite infection. I surveyed the endangered Saltmarsh Sparrow (Ammodramus caudacutus), a species with high exposure to mercury, for malaria parasites. Specifically, I investigated the presence, diversity, and distribution of malaria parasites in the species, the degree of sharing of parasite lineages with other bird species, and the relationship between blood mercury levels and infection status. Through collaboration with researchers at the Biodiversity Research Institute (BRI) and the University of New Hampshire (UNH), blood samples were collected from 290 individuals across the entire breeding range of the species from Maine to Maryland, U.S. By sensitive nested PCR methods, I screened each sample for malaria parasite infection and each positive infection was sequenced at the mitochondrial cytochrome b gene to identify parasite lineages, the standard gene used in defining Plasmodium lineages. Overall, 16.5% of Saltmarsh Sparrows were found to be infected with a total of six Plasmodium lineages. Prevalence and diversity of parasite lineages varied across the breeding range of the Saltmarsh Sparrow, with greater prevalence and diversity in northern states. The skewed distribution of prevalence and parasite diversity may be due to mosquito control measures, habitat type, or possibly climate change. All six parasite lineages were found to be shared with other passerine species including those also found to nest in or near saltmarshes. Blood mercury levels varied in the Saltmarsh Sparrow, ranging from 0.18 ppm to 2.52 ppm with a mean of 0.86 ppm. Although a positive correlation was expected between blood mercury levels and infection status because mercury negatively impacts an individual’s ability to fight infection, I found a negative correlation. These results suggest that individuals with low blood mercury levels are more likely to be infected with malaria parasites. The discovery of a relatively high prevalence and diversity of malaria parasites in the Saltmarsh Sparrow, a species in rapid decline across its range, and the negative correlation relationship between mercury exposure and malaria parasite infection status, suggest the need for continued study of malaria parasite dynamics in the species. Further research will help elucidate the link between environmental pollution and infectious disease risk, which is a pressing topic as environmental contamination combined with climate change may heavily impact host, vector, and parasite distributions and host-parasite dynamics

Convergence towards a European strategic culture? A constructivist framework for explaining changing norms.

The article contributes to the debate about the emergence of a European strategic culture to underpin a European Security and Defence Policy. Noting both conceptual and empirical weaknesses in the literature, the article disaggregates the concept of strategic culture and focuses on four types of norms concerning the means and ends for the use of force. The study argues that national strategic cultures are less resistant to change than commonly thought and that they have been subject to three types of learning pressures since 1989: changing threat perceptions, institutional socialization, and mediatized crisis learning. The combined effect of these mechanisms would be a process of convergence with regard to strategic norms prevalent in current EU countries. If the outlined hypotheses can be substantiated by further research the implications for ESDP are positive, especially if the EU acts cautiously in those cases which involve norms that are not yet sufficiently shared across countries

A meta-study of relationships between fluvial channel-body stacking pattern and aggradation rate: implications for sequence stratigraphy

A quantitative comparison of 20 literature case studies of fluvial sedimentary successions tests common assumptions made in published models of alluvial architecture concerning (1) inverse proportionality between channel-deposit density and floodplain aggradation rates, and (2) resulting characteristics of channel-body geometries and connectedness. Our results do not support the relationships predicted by established stratigraphy models: the data suggest that channel-body density, geometry, and stacking pattern are not reliable diagnostic indicators of rates of accommodation creation. Hence, these architectural characteristics alone do not permit the definition of accommodation-based “systems tracts” and “settings”, and this calls into question current sequence stratigraphic practice in application to fluvial successions

The bodily presence of significant others: Intensive care patients' experiences in a situation of critical illness

This study is about intensive care patients and the bodily presence of significant others. The aim of the study is to inquire and understand the patients experience of the body in relation to their significant others during critical illness. Open, unstructured, in-depth interviews with six former intensive care patients provide the data for the study. The phenomenological–hermeneutical analysis points to a theme among ICU patients' experience of conflict between proximity and distance during the bodily presence of their relations. Patients experience different and conflicting forms of responses to the presence of their significant others. Patients experience significant positive confirmation but also negation through this presence. In the ICU situation, the reactions of significant others appear difficult to deal with, yet the physical presence is significant for establishing a sense of affinity. Patients seek to take some responsibility for themselves as well as for their relatives, and are met with a whole spectrum of reactions. Intensive care patients experience the need to be actively, physically present, which often creates sharp opposition between their personal needs and the needs of their significant others for active participation

Electrical impedance tomography system: an open access circuit design

BACKGROUND: This paper reports a simple 2-D system for electrical impedance tomography EIT, which works efficiently and is low cost. The system has been developed in the Sharif University of Technology Tehran-Iran (for the author's MSc Project). METHODS: The EIT system consists of a PC in which an I/O card is installed with an external current generator, a multiplexer, a power supply and a phantom with an array of electrodes. The measurement system provides 12-bit accuracy and hence, suitable data acquisition software has been prepared accordingly. The synchronous phase detection method has been implemented for voltage measurement. Different methods of image reconstruction have been used with this instrument to generate electrical conductivity images. RESULTS: The results of simulation and real measurement of the system are presented. The reconstruction programs were written in MATLAB and the data acquisition software in C++. The system has been tested with both static and dynamic mode in a 2-D domain. Better results have been produced in the dynamic mode of operation, due to the cancellation of errors. CONCLUSION: In the spirit of open access publication the design details of this simple EIT system are made available here

Skin Impedance Measurements for Acupuncture Research: Development of a Continuous Recording System

Skin impedance at acupuncture points (APs) has been used as a diagnostic/therapeutic aid for more than 50 years. Currently, researchers are evaluating the electrophysiologic properties of APs as a possible means of understanding acupuncture's mechanism. To comprehensively assess the diagnostic, therapeutic and mechanistic implications of acupuncture point skin impedance, a device capable of reliably recording impedances from 100 kΩ to 50 MΩ at multiple APs over extended time periods is needed. This article describes design considerations, development and testing of a single channel skin impedance system (hardware, control software and customized electrodes). The system was tested for accuracy against known resistors and capacitors. Two electrodes (the AMI and the ORI) were compared for reliability of recording over 30 min. Two APs (LU 9 and PC 6) and a nearby non-AP site were measured simultaneously in four individuals for 60 min. Our measurement system performed accurately (within 5%) against known resistors (580 kΩ–10 MΩ) and capacitors (10 nF–150 nF). Both the AMI electrode and the modified ORI electrode recorded skin impedance reliably on the volar surface of the forearm (r = 0.87 and r = 0.79, respectively). In four of four volunteers tested, skin impedance at LU 9 was less than at the nearby non-AP site. In three of four volunteers skin impedance was less at PC 6 than at the nearby non-AP site. We conclude that our system is a suitable device upon which we can develop a fully automated multi-channel device capable of recording skin impedance at multiple APs simultaneously over 24 h