Self-Rotation of Cells in an Irrotational AC E-Field in an Opto-Electrokinetics Chip

The use of optical dielectrophoresis (ODEP) to manipulate microparticles and biological cells has become increasingly popular due to its tremendous flexibility in providing reconfigurable electrode patterns and flow channels. ODEP enables the parallel and free manipulation of small particles on a photoconductive surface on which light is projected, thus eliminating the need for complex electrode design and fabrication processes. In this paper, we demonstrate that mouse cells comprising melan-a cells, RAW 267.4 macrophage cells, peripheral white blood cells and lymphocytes, can be manipulated in an opto-electrokinetics (OEK) device with appropriate DEP parameters. Our OEK device generates a non-rotating electric field and exerts a localized DEP force on optical electrodes. Hitherto, we are the first group to report that among all the cells investigated, melan-a cells, lymphocytes and white blood cells were found to undergo self-rotation in the device in the presence of a DEP force. The rotational speed of the cells depended on the voltage and frequency applied and the cells'' distance from the optical center. We discuss a possible mechanism for explaining this new observation of induced self-rotation based on the physical properties of cells. We believe that this rotation phenomenon can be used to identify cell type and to elucidate the dielectric and physical properties of cells.     

Bisalbuminemia in an amphibian

Improved electrophoretic resolution revealed two albumin-like proteins in Taricha granulosa plasma (bisalbuminemia). The Taricha proteins were compared to mammalian, avian and reptilian serum albumins regarding molecular weight, amino acid composition, isoelectric character, solubility and the binding of hemin and dyes. The results indicate that although the two Taricha proteins have demonstrated hemoglobin-binding ability, they possess traits that characterize them to be true serum albumins.     

Censoring in an epidemic with an application to hemophilia-associated AIDS

In epidemiologic studies of infectious diseases, the times of infection may be known only up to an interval. A two-stage parametric regression model is proposed for the analysis of cohort studies during an epidemic in which the exact times of infection cannot be ascertained. The methods permit joint estimation of the effects of covariates both on the risk of infection and the risk of progression to clinical disease once infected. The methodology is applied to a cohort of hemophiliacs who were at risk of infection with the AIDS virus. It was found that hemophiliacs with severe Type A hemophilia were at highest risk of infection, and the risk of infection increased sharply in the early 1980s. Hemophiliacs who were over the age of 20 at infection were at higher risk of progression to AIDS than hemophiliacs who were under age 20. The estimate of the cumulative probability of developing AIDS within t years of infection (the incubation period distribution) for hemophiliacs over age 20 was 1 - exp(-.0021t2.516). Since follow-up in this cohort was restricted to about 10 years from infection, estimates of the incubation period distribution beyond 10 years depend on model extrapolation and should be interpreted cautiously.     

Controlling tungiasis in an impoverished community: an intervention study

Background

In Brazil, tungiasis is endemic in some resource-poor communities where various domestic and sylvatic animals act as reservoirs for this zoonosis. To determine the effect of control measures on the prevalence and intensity of infestation of human and animal tungiasis, a repeated cross-sectional survey with intervention was carried out.

Methodology/Principal Findings

In a traditional fishing community in Northeast Brazil, humans and reservoir animals were treated, and premise-spraying using an insecticide was done, while a second fishing community served as a control. Both communities were followed up 10 times during a 12-month period. At baseline, prevalence of tungiasis was 43% (95% confidence interval [CI]: 35%–51%) and 37% (95% CI: 31%–43%) in control and intervention villages, respectively. During the study, prevalence of tungiasis dropped to 10% (95% CI: 8%–13%; p<0.001) in the intervention village, while the prevalence remained at a high level in the control village. However, after one year, at the end of the study, in both communities the prevalence of the infestation had reached pre-intervention levels. Whereas the intensity of infestation was significantly reduced in the intervention community (p<0.001), and remained low at the end of the study (p<0.001), it did not change in the control village.

Conclusion/Significance

Our study shows that a reduction of prevalence and intensity of infestation is possible, but in impoverished communities a long-lasting reduction of disease occurrence can only be achieved by the regular treatment of infested humans, the elimination of animal reservoirs, and, likely, through environmental changes.

Trial Registration

Controlled-Trials.com ISRCTN27670575     

Mechanosensitivity as an integrative system in heart: an audit

This review examines a manifold of apparently loosely linked observations and mechanisms, from membrane to man, and assembles them to support the notion that mechanoelectric transduction is an integrative regulatory system in the heart. For this, the assemblage has to satisfy, at least to some extent, criteria that apply to other integrative regulatory systems such as the endocrine and nervous systems. The integrative effectors in the endocrine system are chemical linkages, circulating hormones: in the nervous system the linkage is a network of cables, nerve conduction and neurotransmitters. Mechanical integration is would be effected through mechanical machinery, cardiac contractile and hydraulic function with attendant stress and strain transmitted via "tensegrity". This can, through the cytoskeleton, begin with membrane integrins and transmit intracellularly for example via F actins to reach the rest of the membranous integrins. Further transmission to the organ is via cell-to-cell adhesion complexes and the extracellular matrix. This tensegrity facilitates integration of force and strain changes from area to area. In consequence, and analogous to the neurendocrine system, mechanoelectric transduction should, and does (1) operate at the molecular or membrane level--this would be via mechanotransducers affecting transmembrane ionic flow; (2) operate in the cell--to influence electrophysiology; (3) have a multicellular expression--e.g. mechanical distortion of one cell can raise intracellular calcium of an adjacent cell; (4) express in the intact organ--e.g. an increase in venous return hydraulically distends the sinoatrial node, steepening its pacemaker potential, thus increasing heart rate. It should also (5) demonstrate elements of a feedback system--"mechanoelectric feedback", and (6) interact with other systems--the cytoskeleton incorporates cell signalling complexes intersecting with other signal cascades. Finally, (7) it can malfunction to produce clinical abnormality--it contributes electrophysiologically to lethal cardiac arrhythmia. This anatomical and functional behaviour of mechanoelectric transduction could sanction the prospect of viewing it as analogous to the other integrative physiological systems.     

Abdominal pain associated with an intra-abdominal gonad in an adult

Controversy still surrounds management of cryptorchidism in adults. Options include orchiectomy, orchiopexy, and close observation. What about fertility if orchiectomy is chosen? How is the risk of cancer affected when observation is the choice? Follow the reasoning for the management strategy for this adult presenting with abdominal pain.     

Species dynamics and colonization patterns in an abandoned forest in an urban landscape

Species dynamics in an abandoned urban forest of Central Japan is described in this paper. The dominant species in the urban plantation were Cryptomeria japonica and Chamaecyparis obtusa. A variety of eight patches of the canopy was produced by previous forest management practices. Progressive and retrogressive species dynamics within these eight patches are investigated in this paper. The study elucidates the deterministic role of patchiness in the nature of species colonization and the maintenance of species diversity in an urban forest. Altogether 139 native and/or naturalized species, including 23 shrub and 35 tree species, were recorded in the study area of 3.2 ha. The performance of species varied according to their successional attributes indicating a selective canopy influence. Twenty percent of the tree species were shade-intolerant pioneers (e.g. Cornus spp., Rhus javanica var. roxburghii) re-established under selective tree-felling. Thirty percent were shade-tolerant climax species (e.g. Neolitsea sericea, Persea thunbergii) dominant in remnant closed patches. The remaining 50% belonged to various seral types with aggressive deciduous species (e.g. Aphananthe aspera, Celtis sinensis) in most of the patches. Some ruderal herbaceous species dominated heavily disturbed clear-felled patches. This study suggests that canopy modification influences the subsequent colonization pattern. Furthermore, heterogeneous patches contribute to greater species diversity and dynamics in isolated woodlands.     

Induced defences in an endangered amphibian in response to an introduced snake predator

Introduced species have contributed significantly to the extinction of endemic species on islands. They also create new selection pressures on their prey that may result in modified life history strategies. Introduced viperine snakes (Natrix maura) have been implicated in the decline of the endemic midwife toad of Mallorca (Alytes muletensis). A comparison of A. muletensis tadpoles in natural pools with and without snakes showed that those populations subject to snake predation possessed longer tails with narrower tail fins but deeper tail muscles. Field and laboratory experiments showed that these changes in tail morphology could be induced by chemical and tactile cues from snakes. Populations of tadpoles that were subject to snake predation also displayed clear bimodal size-frequency distributions, with intermediate-sized tadpoles missing from the pools completely. Tadpoles in pools frequented by snakes developed faster in relation to their body size than those in pools without snakes. Variation in morphology between toad populations may therefore be caused by a combination of size-selective predation and tadpole plasticity. The results of this study indicate that the introduction of alien species can result in selection for induced defences, which may facilitate coexistence between predator and prey under certain conditions.     

Rapid evolution of a novel song and an increase in repertoire size in an island population of an Australian songbird

Cultural innovations are commonly noted in animals, but times of development of novel traits are usually unknown. We report here a novel song type arising in a bird population on an offshore island of Western Australia where the time of colonization of the island by the Western Gerygone Gerygone fusca is known. On the mainland, a single song type is widespread. On Rottnest Island, many individuals sing a different type of song and a number possess a repertoire of two song types: the standard song shared with the mainland and the novel song type not found on the neighbouring mainland. The novel song type found on Rottnest is so different in its syntactical structure that one could easily mistake it for that of a new species. The characteristic song of mainland birds is irregular in the frequencies at which the notes within a song are delivered. The novel song on Rottnest has a highly structured syntax with notes delivered at a strict and repeated sequence of frequencies resulting in a rhythmic musical sound. The species is known to have colonized Rottnest in about 1955. The new song type apparently developed rapidly by cultural evolution in the last 50 years.