Dual shape recovery of red blood cells flowing out of a microfluidic constriction

Micropipette aspiration, optical tweezers, rheometry, or ecktacytometry have been used to study the shape recovery of healthy human Red Blood Cells (RBCs) and measure associated relaxation times of the order of 100-300 ms. These measurements are in good agreement with the Kelvin-Voigt model, which describes the cell as a visco-elastic material, predicting that its relaxation time only depends on cell intrinsic properties. However, such mechanical solicitation techniques are far from being relevant regarding RBC solicitation in vivo. In this paper, we report for the first time the existence of two different behaviors of the RBC shape recovery while flowing out of a microfluidic constricted channel. The calculation of the viscous stress corresponding to the frontier between the two recovery modes confirms that the RBC resistance to shear μ is the elastic property dominating the transition between the two recovery behaviors. We also quantified associated recovery times τ r and report values as low as 4 ms-which is almost two decades smaller than the typical RBC relaxation time-at high viscosity and flow velocity of the carrier fluid. Although we cannot talk about relaxation time because the cell is never at rest, we believe that the measured shape recovery time arises from the coupling of the cell intrinsic deformability and the hydrodynamic stress. Depending on the flow conditions, the cell mechanics becomes dominant and drives the shape recovery process, allowing the measurement of recovery times of the same order of magnitude than relaxation times previously published. Finally, we demonstrated that the measurement of the shape recovery time can be used to distinguish Plasmodium falciparum (causing malaria) infected RBCs from healthy RBCs.

Effect of electrode material on the sensitivity of interdigitated electrodes used for Electrical Cell-Substrate Impedance Sensing technology

This study explores the effect of the electrode material on the sensitivity of interdigitated electrodes (IDEs) used in Electrical Cell-Substrate Impedance Sensing (ECIS) technology. This technique is a label-free method to evaluate cellular activity of adherent cells. IDEs of gold (Au), indium tin oxide (ITO) and ITO functionalized with iridium oxide (IrO_x) were characterized with impedance spectroscopy and their interfacial impedances were evaluated in potassium chloride (KCl) solutions. In parallel, ECIS measurements were performed on these three electrode materials during the proliferation of the human breast cancer cell line, MCF-7. The results indicate that the difference in sensitivity to MCF-7 of the three materials might be strongly correlated to their interfacial impedances. We found that ITO electrodes coated with IrO_x show slightly higher sensitivity to MCF-7 breast cancer cells while still offering transparency compared to gold, which is considered the conventional material in ECIS devices.

Determination of Red Blood Cell fatigue using electrodeformation

In this work, we used electrodeformation (ED) [1] as a new strategy to evaluate the fatigue of healthy human Red Blood Cells (RBCs). Using dielectrophoresis (DEP) forces, we submitted RBCs to a series of elongation and relaxation cycles to model their mechanical stress in the blood circulation and we used their relaxation time as a marker to evaluate their fatigue. In this paper, we first investigated the dependency of the RBC mechanical response upon the experimental parameters, such as the viscosity η_out of the external medium, the amplitude ΔV of the applied voltage, the duration of the solicitation t_sol, the number of solicitations N as well as the resting time t_rest between two solicitations. The impact of these parameters was evaluated through the analysis of both RBC deformation index D and relaxation time τ. Finally, the optimization of these parameters was used to monitor RBC fatigue.

Effect of electrode material on the sensitivity of interdigitated electrodes used for Electrical Cell-Substrate Impedance Sensing technology

This study explores the effect of the electrode material on the sensitivity of interdigitated electrodes (IDEs) used in Electrical Cell-Substrate Impedance Sensing (ECIS) technology. This technique is a label-free method to evaluate cellular activity of adherent cells. IDEs of gold (Au), indium tin oxide (ITO) and ITO functionalized with iridium oxide (IrO_x) were characterized with impedance spectroscopy and their interfacial impedances were evaluated in potassium chloride (KCl) solutions. In parallel, ECIS measurements were performed on these three electrode materials during the proliferation of the human breast cancer cell line, MCF-7. The results indicate that the difference in sensitivity to MCF-7 of the three materials might be strongly correlated to their interfacial impedances. We found that ITO electrodes coated with IrO_x show slightly higher sensitivity to MCF-7 breast cancer cells while still offering transparency compared to gold, which is considered the conventional material in ECIS devices.

A passive microfluidic device for plasma extraction from whole human blood

Promising microfluidic devices are proposed herein to continuously and passively extract plasma from whole human blood. These designs are based on the red cells lateral migration and the resulting cell-free layer locally expanded by geometric singularities, such as an abrupt enlargement of the channel or a cavity adjacent to the channel. After an explanation of flow patterns, devices are experimentally and biologically validated for plasma extraction. They are also successively optimized with extraction yields up to 17.8% for a 1:20 blood injected at 100 microL/min.

[Painful edema of the feet revealing ankylosing spondylitis]

INTRODUCTION

Painful peripheral oligoarthritis can reveal ankylosing spondylitis. In some instances, an acral pitting edema can be the sign of this affection.

CASE REPORT

A 39-year-old man, with no significant previous medical history, consulted in a dermatology department for acral pain and edema of both feet, which were exacerbated during the second part of the night. On examination, he had a pitting edema and a livedo of the distal part of the feet. Biological investigations revealed an inflammatory syndrome and the presence of the histocompatibility HLA-B27 antigen. Bone scintigraphy revealed distal hyperfixation on both feet. Diagnosis of ankylosing spondylitis was established.

DISCUSSION

Late-onset ankylosing spondylitis, which appears in subjects older than 35 years, can manifest as peripheral arthritis with systemic signs, often in the absence of involvement of the axial skeleton. Peripheral pitting edema of lower limbs can be the presenting sign. Since cutaneous involvement can be the presenting sign, dermatologists should be aware of this entity.

Improving the comparative map of SSC2p-q13 by sample sequencing of BAC clones

To improve the comparative map for pig chromosome 2 and increase the gene density on this chromosome, a porcine bacterial artificial chromosome (BAC) library was screened with 17 microsatellite markers and 18 genes previously assigned to pig chromosome 2. Fifty-one BAC clones located in the region of a maternally imprinted quantitative trait locus for backfat thickness (BFT) were identified. From these BACs 372 kb were sample sequenced. The average read length of a subclone was 442 basepair (bp). Contig assembly analysis showed that every bp was sequenced 1.28 times. Subsequently, sequences were compared with sequences in the nucleotide databases to identify homology with other mammalian sequences. Sequence identity was observed with sequences derived from 35 BACs. The average percentage identity with human sequences was 87.6%, with an average length of 143 bp. In total, sample sequencing of all BACs resulted in sequence identity with 29 human genes, 13 human expressed sequence tags (ESTs), 17 human genomic clones, one rat gene, one porcine gene and nine porcine ESTs. Eighteen genes located on human chromosome 11 and 19, and seven genes from other human locations, one rat gene and one porcine gene were assigned to pig chromosome 2 for the first time. The new genes were added to the radiation hybrid map at the same position as the locus from which the BAC that was sequenced was derived. In total 57 genes were placed on the radiation hybrid map of SSC2p-q13.

A high-resolution comparative RH map of porcine chromosome (SSC) 2

A high-resolution comparative map was constructed for porcine Chromosome (SSC) 2, where a QTL for back fat thickness (BFT) is located. A radiation hybrid (RH) map containing 33 genes and 25 microsatellite markers was constructed for this chromosome with a 3000-rad porcine RH panel. In total, 16 genes from human Chromosome (HSA) 11p, HSA19p, and HSA5q were newly assigned to SSC2. One linkage group was observed at LOD 3.0, and five linkage groups at LOD 4.0. Comparison of the porcine RH map with homologous human gene orders identified four conserved segments between SSC2 and HSA11, HSA19, and HSA5. Concerning HSA11, a rearrangement of gene order is observed. The segment HSA11p15.4-q13 is inverted on SSC2 when compared with the distal tip of SSC2p, which is homologous to HSA11p15.5. The boundaries of the conserved segments between human and pig were defined more precisely. This high-resolution comparative map will be a valuable tool for further fine mapping of the QTL area.

Fine mapping and imprinting analysis for fatness trait QTLs in pigs

Quantitative trait loci (QTL) for fatness traits were reported recently in an experimental Meishan x Large White and Landrace F(2) cross. To further investigate the regions on pig Chr 2 (SSC2), SSC4, and SSC7, 25 additional markers from these regions were typed on 800 animals (619 F(2) animals, their F(1) parents, and F(0) grandfathers). Compared with the published maps, a modified order of markers was observed for SSC4 and SSC7. QTL analyses were performed both within the half-sib families as well as across families (line cross). Furthermore, a QTL model accounting for imprinting effects was tested. Information content could be increased considerably on all three chromosomes. Evidence for the backfat thickness QTL on SSC7 was increased, and the location could be reduced to a 33-cM confidence interval. The QTL for intramuscular fat on SSC4 could not be detected in this half-sib analysis, whereas under the line cross model a suggestive QTL on a different position on SSC4 was detected. For SSC2, in the half-sib analysis, a suggestive QTL for backfat thickness was detected with the best position at 26 cM. Imprinting analysis, however, revealed a genome-wise, significant, paternally expressed QTL on SSC2 with the best position at 63 cM. Our results suggest that this QTL is different from the previously reported paternally expressed QTL for muscle mass and fat deposition on the distal tip of SSC2p.

[Optic disk drusen and intracranial tumor]

A fifty-one year old woman with a Lindau sickness presented bilateral optic disc swelling and peripapillary haemorrhage. Intracranial hypertension was suspected. Perimetry, echography and fluorescein fundus angiography revealed optic disc drusen.

Aspirin and gastrointestional bleeding. Interest of plasma salicylate determination

From history-taking and from analysis of plasma salicylate levels it is shown that a link exists between aspirin and gastrointestinal bleeding in 68% of cases. Salicylate levels alone indicate that aspirin has been taken in 22% of cases. Plasma salicylate measurement and endoscopy allow a better understanding of haemorrhagic lesions due to aspirin. Aspirin is responsible especially for haemorrhage from ulcers and acute gastritis or duodenitis. Aspirin is seen to be dangerous in a moderate number of susceptible individuals: those with peptic ulcer constitution or cirrhosis.

[Anaphylactic accidents due to glaphenine. 5 cases]

The authors report 5 cases of shock type anaphylactic reactions after the ingestion of glafenine. Up to the present, acute tubulo-interstitial nephritis had chiefly been reported. The existence of allergy to this medication remains to be proved by the wider application of allergological studies.