Nanoscale surface topography reshapes neuronal growth in culture

Neurons are sensitive to topographical cues provided either by in vivo or in vitro environments on the micrometric scale. We have explored the role of randomly distributed silicon nanopillars on primary hippocampal neurite elongation and axonal differentiation. We observed that neurons adhere on the upper part of nanopillars with a typical distance between adhesion points of about 500 nm. These neurons produce fewer neurites, elongate faster, and differentiate an axon earlier than those grown on flat silicon surfaces. Moreover, when confronted with a differential surface topography, neurons specify an axon preferentially on nanopillars. As a whole, these results highlight the influence of the physical environment in many aspects of neuronal growth.

Intracellular stresses in patterned cell assemblies

Confining cells on adhesive patterns allows performing robust, weakly dispersed, statistical analysis. A priori, adhesive patterns could be efficient tools to analyze intracellular cell stress fields, in particular when patterns are used to force the geometry of the cytoskeleton. This tool could then be very helpful in deciphering the relationship between the internal architecture of the cells and the mechanical, intracellular stresses. However, the quantification of the intracellular stresses is still something delicate to perform. Here we first propose a new, very simple and original method to quantify the intracellular stresses, which directly relates the strain the cells impose on the extracellular matrix to the intracellular stress field. This method is used to analyze how confinement influences the intracellular stress field. As a result, we show that the more confined the cells are, the more stressed they will be. The influence of the geometry of the adhesive patterns on the stress patterns is also discussed.

The FEN1 E359K germline mutation disrupts the FEN1-WRN interaction and FEN1 GEN activity, causing aneuploidy-associated cancers

Polymorphisms and somatic mutations in Flap Endonuclease 1 (FEN1), an essential enzyme involved in DNA replication and repair, can lead to functional deficiencies of the FEN1 protein and a predisposition to cancer. We identified a FEN1 germline mutation which changed residue E359 to K in a patient whose family had a history of breast cancer. We determined that the E359K mutation, which is in the protein-protein domain of FEN1, abolished the interaction of FEN1 with Werner Syndrome protein (WRN), an interaction which is critical for resolving stalled DNA replication forks. Furthermore, although the flap endonuclease activity of FEN1 E359K was unaffected, it failed to resolve bubble structures, which requires the FEN1 gap dependent endonuclease (GEN) activity. To determine the etiological significance of E359K, we established a mouse model containing this mutation. E359K mouse embryonic fibroblasts (MEF) were more sensitive to DNA cross-linking agents that cause replication forks to stall. Cytological analysis suggested that the FEN1-WRN interaction was also required to for telomere stability; mutant cell lines had fragile telomeres, increased numbers of spontaneous chromosomal anomalies and higher frequencies of transformation. Moreover, the incidence of cancer was significantly higher in mice homozygous for FEN1 E359K than in wild-type mice, suggesting that the FEN1 E359K mutation is oncogenic.

Reversible optical memory for twisted photons

We report on an experiment in which orbital angular momentum (OAM) of light is mapped at the single-photon level into and out of a cold atomic ensemble. Based on the dynamic electromagnetically induced transparency protocol, the demonstrated optical memory enables the reversible mapping of Laguerre-Gaussian modes with preserved handedness of the helical phase structure. The demonstrated capability opens the possibility to the storage of qubits encoded as superpositions of OAM states and to multidimensional light matter interfacing.

Physically based principles of cell adhesion mechanosensitivity in tissues

The minimal structural unit that defines living organisms is a single cell. By proliferating and mechanically interacting with each other, cells can build complex organization such as tissues that ultimately organize into even more complex multicellular living organisms, such as mammals, composed of billions of single cells interacting with each other. As opposed to passive materials, living cells actively respond to the mechanical perturbations occurring in their environment. Tissue cell adhesion to its surrounding extracellular matrix or to neighbors is an example of a biological process that adapts to physical cues. The adhesion of tissue cells to their surrounding medium induces the generation of intracellular contraction forces whose amplitude adapts to the mechanical properties of the environment. In turn, solicitation of adhering cells with physical forces, such as blood flow shearing the layer of endothelial cells in the lumen of arteries, reinforces cell adhesion and impacts cell contractility. In biological terms, the sensing of physical signals is transduced into biochemical signaling events that guide cellular responses such as cell differentiation, cell growth and cell death. Regarding the biological and developmental consequences of cell adaptation to mechanical perturbations, understanding mechanotransduction in tissue cell adhesion appears as an important step in numerous fields of biology, such as cancer, regenerative medicine or tissue bioengineering for instance. Physicists were first tempted to view cell adhesion as the wetting transition of a soft bag having a complex, adhesive interaction with the surface. But surprising responses of tissue cell adhesion to mechanical cues challenged this view. This, however, did not exclude that cell adhesion could be understood in physical terms. It meant that new models and descriptions had to be created specifically for these biological issues, and could not straightforwardly be adapted from dead matter. In this review, we present physical concepts of tissue cell adhesion and the unexpected cellular responses to mechanical cues such as external forces and stiffness sensing. We show how biophysical approaches, both experimentally and theoretically, have contributed to our understanding of the regulation of cellular functions through physical force sensing mechanisms. Finally, we discuss the different physical models that could explain how tissue cell adhesion and force sensing can be coupled to internal mechanosensitive processes within the cell body.

Epithelial protein lost in neoplasm (EPLIN) interacts with α-catenin and actin filaments in endothelial cells and stabilizes vascular capillary network in vitro

Adherens junctions are required for vascular endothelium integrity. These structures are formed by the clustering of the homophilic adhesive protein VE-cadherin, which recruits intracellular partners, such as β- and α-catenins, vinculin, and actin filaments. The dogma according to which α-catenin bridges cadherin·β-catenin complexes to the actin cytoskeleton has been challenged during the past few years, and the link between the VE-cadherin·catenin complex and the actin cytoskeleton remains unclear. Recently, epithelial protein lost in neoplasm (EPLIN) has been proposed as a possible bond between the E-cadherin·catenin complex and actin in epithelial cells. Herein, we show that EPLIN is expressed at similar levels in endothelial and epithelial cells and is located at interendothelial junctions in confluent cells. Co-immunoprecipitation and GST pulldown experiments provided evidence that EPLIN interacts directly with α-catenin and tethers the VE-cadherin·catenin complex to the actin cytoskeleton. In the absence of EPLIN, vinculin was delocalized from the junctions. Furthermore, suppression of actomyosin tension using blebbistatin triggered a similar vinculin delocalization from the junctions. In a Matrigel assay, EPLIN-depleted endothelial cells exhibited a reduced capacity to form pseudocapillary networks because of numerous breakage events. In conclusion, we propose a model in which EPLIN establishes a link between the cadherin·catenin complex and actin that is independent of actomyosin tension. This link acts as a mechanotransmitter, allowing vinculin binding to α-catenin and formation of a secondary molecular bond between the adherens complex and the cytoskeleton through vinculin. In addition, we provide evidence that the EPLIN clutch is necessary for stabilization of capillary structures in an angiogenesis model.

Detection of hazardous weight-loss substances in adulterated slimming formulations using ultra-high-pressure liquid chromatography with diode-array detection

The presence on the market of illegal products for slimming purposes or the treatment of overweight is a public health issue. These products may contain illicit chemicals in order to improve their effectiveness. Some of these weight-loss compounds are responsible for adverse events, including fatal outcomes. A general strategy for the analysis of any suspect formulation begins with a large screening for the general search of a wide range of compounds. A methodology for the qualitative and quantitative determination of 34 compounds in slimming preparations (such as dietary supplements or medicinal products) was used for the control of slimming formulations from the market, including over the Internet. The fast liquid chromatography system (ultra-high-pressure liquid chromatography) used a gradient of solvent (phosphate buffer and acetonitrile), a C18 endcapped column and a diode array detector. This system allows dual identification based on retention time and UV spectra. The analytical method is simple, fast and selective since 34 weight-loss compounds can be detected in a 15-min run time. Thus, 32 commercial slimming formulations were analysed using this method, allowing the detection and quantification of hazardous active substances: caffeine, clenbuterol, nicotinamide, phenolphthalein, rimonabant, sibutramine, didesmethylsibutramine, synephrine and yohimbine.

Minimal encounter time and separation determine ligand-receptor binding in cell adhesion

The binding properties of biomolecules play a crucial role in many biological phenomena, especially cell adhesion. Whereas the attachment kinetics of soluble proteins is considered well known, complex behavior arises when protein molecules are bound to the cell membrane. We probe the hidden kinetics of ligand-receptor bond formation using single-molecule flow chamber assays and Brownian dynamics simulations. We show that, consistent with our recently proposed hypothesis, association requires a minimum duration of contact between the reactive species. In our experiments, ICAM-1 anchored on a flat substrate binds to anti-ICAM-1 coated onto flowing microbeads. The interaction potential between bead and substrate is measured by microinterferometry and is used as an ingredient to simulate bead movement. Our simulation calculates the duration of ligand-receptor contacts imposed by the bead movement. We quantitatively predict the reduction of adhesion probability measured for shorter tether length of the ligand or if a repulsive hyaluronan layer is added onto the surface. To account for our results, we propose that bond formation may occur in our system by crossing of a diffusive plateau in the energy landscape, on the timescale of 5 ms and an energy barrier of 5 k(B)T, before reaching the first detectable bound state. Our results show how to relate cell-scale behavior to the combined information of molecular reactivity and biomolecule submicron-scale environment.

XUTs are a class of Xrn1-sensitive antisense regulatory non-coding RNA in yeast

Non-coding (nc)RNAs are key players in numerous biological processes such as gene regulation, chromatin domain formation and genome stability. Large ncRNAs interact with histone modifiers and are involved in cancer development, X-chromosome inactivation and autosomal gene imprinting. However, despite recent evidence showing that pervasive transcription is more widespread than previously thought, only a few examples mediating gene regulation in eukaryotes have been described. In Saccharomyces cerevisiae, the bona-fide regulatory ncRNAs are destabilized by the Xrn1 5'-3' RNA exonuclease (also known as Kem1), but the genome-wide characterization of the entire regulatory ncRNA family remains elusive. Here, using strand-specific RNA sequencing (RNA-seq), we identify a novel class of 1,658 Xrn1-sensitive unstable transcripts (XUTs) in which 66% are antisense to open reading frames. These transcripts are polyadenylated and RNA polymerase II (RNAPII)-dependent. The majority of XUTs strongly accumulate in lithium-containing media, indicating that they might have a role in adaptive responses to changes in growth conditions. Notably, RNAPII chromatin immunoprecipitation followed by DNA sequencing (ChIP-seq) analysis of Xrn1-deficient strains revealed a significant decrease of RNAPII occupancy over 273 genes with antisense XUTs. These genes show an unusual bias for H3K4me3 marks and require the Set1 histone H3 lysine 4 methyl-transferase for silencing. Furthermore, abolishing H3K4me3 triggers the silencing of other genes with antisense XUTs, supporting a model in which H3K4me3 antagonizes antisense ncRNA repressive activity. Our results demonstrate that antisense ncRNA-mediated regulation is a general regulatory pathway for gene expression in S. cerevisiae.

Large Heterologies Impose Their Gene Conversion Pattern onto Closely Linked Point Mutations

We have studied the meiotic non-Mendelian segregation (NMS) pattern of seven large heterologous combinations located in the b2 ascospore gene of Ascobolus. The NMS patterns of these aberration heterozygotes widely differ from each other and from those of point mutations located in the same genetic region. They give lower gene conversion frequencies than point mutations, no postmeiotic segregations (PMS), and either parity or disparity that favors the wild type allele. Two related deletions, G234 and G40, were studied for their effects on the conversion behavior of closely linked point mutations. We found that, when heterozygous, the deletions impose their own NMS pattern onto close mutations. These effects occur on both sides of the heterologies. The effects upon PMS and disparity of linked point mutations gradually disappear as point mutations become more distant. The effects on NMS frequencies and on aberrant 4:4 are polar. They persist for all mutations located downstream from the high conversion end of the gene. This last effect can reflect a blockage of symmetric hDNA formation by large heterologies, whereas the epistasis of the NMS pattern of large heterologies over that of closely linked point mutations suggests that large heterologies and point mutations undergo conversion by means of distinct pathways.

[Dreaming is a hypnic state of consciousness: getting rid of the Goblot hypothesis and its modern avatars]

SUMMARY

In the late nineteenth century, French logician Edmond Goblot first hypothesized that dreaming occurred at the moment of awakening only. Revisiting--more or less directly--Goblot's hypothesis, several contemporary authors have since renewed this unusual claim that oniric experience does not occur during sleep. So did some influential analytical philosophers (Wittgenstein, Malcolm, Dennett), with their typical formalism, and famous dream researcher Calvin Hall, who tried to provide experimental evidence for the Goblot's hypothesis. More recently, French neurobiologist Jean-Pol Tassin claimed, on the basis of controversial neurobiological and cognitive principles, that only awakening gives rise to a dream, by instantaneous shaping of information issuing of neural networks activated during preceding sleep. Actually, numerous and robust experimental data in sleep psychophysiology clearly rule out Goblot's hypothesis and its modern avatars. Thus, results of studies using nocturnal awakenings (with or without preceding hypnic stimulation), as well as observations of onirical behaviours (like rapid eye movement sleep behavior disorders, or voluntary movements of lucid dreamers) demonstrate that dreaming definitely occurs during sleep. Actually, cortical evoked potentials can be observed during sleep, which likely reflect controlled cognitive processes. Dreaming is a hypnic state of consciousness, and seems to represent a sleep thought which, although uneasily accessible, is nevertheless open to psychological investigation.

Frantz's tumor: is mutilating surgery always justified in young patients?

BACKGROUND

Solid pseudopapillary tumor (Frantz's tumor) of the pancreas is a rare lesion. It is of low-grade malignancy but can cause extensive local invasion. The aim of this study was to assess the outcome of Frantz's tumors after incomplete resection.

METHODS

We contacted all authors who published case reports describing incomplete resection of Frantz's tumor between 1985 and 2008 to request follow-up information.

RESULTS

Follow-up information was obtained for 11 out 18 patients who underwent incomplete resection. Estimated median survival rate was 5.7 years (69.5 months).

CONCLUSION

Since Frantz's tumor typically develops mainly in children and young women, a 5.7 year survival rate is unacceptable. Thus complete resection of locally invasive solid-pseudopapillary tumor of the pancreas is always justified, even at the price of difficult, mutilating surgery.

Time‐of‐Day Effects on Myoelectric and Mechanical Properties of Muscle During Maximal and Prolonged Isokinetic Exercise

The aim of this study was to examine the time-of-day (TOD) effects in myoelectric and mechanical properties of muscle during a maximal and prolonged isokinetic exercise. Twelve male subjects were asked to perform 50 maximal voluntary contractions (MVC) of the knee extensor muscles at a constant angular velocity of 2.09 rad . sec(-1), at 06 : 00 and 18 : 00 h. Torque and electromyographic (EMG) parameters were recorded for each contraction, and the ratio between these values was calculated to evaluate variations of the neuromuscular efficiency (NME) with fatigue and with TOD. The results indicated that maximal torque values (T(45)Max) was significantly higher (7.73%) in the evening than in the morning (p<0.003). The diurnal variation in torque decrease was used to define two phases. During the first phase (1st to the 26th repetition), torque values decreased fast and values were higher in the evening than in the morning, and during the second phase (27th to the 50th repetition), torque decreased slightly and reached a floor value that appeared constant with TOD. The EMG parameters (Root Mean Square; RMS) were modified with fatigue, but were not TOD dependent. The NME decrease-significantly with fatigue, showing that peripheral factors were mainly involved in the torque decrease. Furthermore, NME decrease was greater at 18 : 00 than at 06 : 00 h for the vastus medialis (p<0.05) and the vastus lateralis muscles (p<0.002), and this occurred during the first fatigue phase of the exercise. In conclusion, the diurnal variation of the muscle fatigue observed during a maximal and prolonged isokinetic exercise seems to reflect on the muscle, with a greater contractile capacity but a higher fatigability in the evening compared to the morning.

Increase of CD4+ CD25+ regulatory T cells in the peripheral blood of patients with metastatic carcinoma: a Phase I clinical trial using cyclophosphamide and immunotherapy to eliminate CD4+ CD25+ T lymphocytes

We determined the number and functional status of CD4+ CD25(high) regulatory T cells (Treg) in blood samples from patients with metastatic carcinoma, and evaluated their sensitivity to a single intravenous infusion of cyclophosphamide. Treg numbers were significantly higher in 49 patients with metastatic cancer (9.2% of CD4+ T cells) compared to 24 healthy donors (7.1%). These cells expressed the transcription factor forkhead box P3 (FoxP3), glucocorticoid-induced tumour necrosis factor receptor family-related protein (GITR) and intracellular CD152, and demonstrated a suppressive activity in vitro against CD4+ CD25- autologous proliferation. At a single intravenous infusion, cyclophosphamide failed, in association with a non-specific immunotherapy by intratumoral bacille Calmette-Guérin (BCG), to modulate significantly Treg numbers or function. Metastatic cancer is associated with an expansion of peripheral blood CD4+ CD25(high) FoxP3+ GITR+ CD152+ Treg cells whose immunosuppressive properties do not differ from those of healthy subjects. Moreover, cyclophosphamide administration may not represent an optimal therapy to eliminate Treg, which further underlines the need to identify specific agents that would selectively deplete these cells.

[Control of the quality of antibiotics in the European Pharmacopoeia: recent development in the case of aminoglycosides]

Aminoglycosides constitute a particular class of antibiotics presenting aminoglycoside moieties linked to a central aminocyclitol ring. Several aminoglycosides are described by a monograph in the European Pharmacopoeia. The related substances test is used to check for impurities. For this purpose, thin layer chromatography is now being replaced by high performance liquid chromatography. In the case of aminoglycosides the main challenge is the detection of these compounds since they do not possess a chromophore in their structure. Different possibilities are proposed in the monographs. Amikacine is detected at 340 nm after pre-column derivatization. In more recent monographs, pulsed amperometry detection is proposed. However, this mode of detection requires skillful manipulations. Evaporative light scattering detection could be a valuable alternative. The advantages and drawbacks of each approach will be discussed.

hSNF5/INI1-deficient tumours and rhabdoid tumours are convergent but not fully overlapping entities

Rhabdoid tumours (RTs) are rare but highly aggressive tumours of childhood. Their rarity and their miscellaneous locations make the diagnosis particularly challenging for pathologists. Central nervous system and peripheral RTs have been associated with biallelic inactivation of the hSNF5/INI1/SMARCB1 (hSNF5/INI1) tumour suppressor gene. Immunohistochemistry (IHC) with a monoclonal anti-hSNF5/INI1 antibody has recently been proposed as an efficient diagnostic tool for RTs. We have conducted a retrospective study of 55 tumours referred to our institution with a suspicion of RT. This analysis included pathological review, IHC with anti-hSNF5/INI1 antibody, and molecular investigation using quantitative DNA fluorescent analysis and sequencing of the nine exons of hSNF5/INI1. The molecular lesion could be detected in 37 of the 39 cases exhibiting negative staining for hSNF5/INI1. In the two discrepant cases, the lack of detection of genetic abnormality was probably owing to the presence of a high number of non-tumour cells in the samples. This indicates that hSNF5/INI1 IHC is very sensitive and highly specific for the detection of hSNF5/INI1 loss-of-function. Among the 38 cases with typical RT histological features, six failed to exhibit hSNF5/INI1 mutation and stained positive for hSNF5/INI1. This strongly supports the evidence of a second genetic locus, distinct from hSNF5/INI1, associated with RT. Conversely, seven tumours with histological features poorly compatible with RT stained negative for hSNF5/INI1; they nevertheless exhibited an age of onset and a clinical behaviour similar to RT. This suggests that hSNF5/INI1 inactivation is not strictly limited to typical RT but characterizes a wider family of hSNF5/INI1-deficient tumours. Consequently, we believe that anti-hSNF5/INI1 IHC should be performed widely, even when the pathological characteristics are not typical. The molecular investigation should be performed in infants when a rhabdoid predisposition syndrome is suspected.

The influence of circadian rhythm during a sustained submaximal exercise and on recovery process

The purpose of this study was to examine the time-of-day effects on muscle fatigue and recovery process following an isometric fatiguing contraction. Sixteen male subjects were tested at two times (06:00h and 18:00h) and were requested to perform a sustained submaximal contraction of the elbow flexors, consisting in maintaining 40% of their absolute strength as long as they could. Isometric maximal voluntary contractions (MVC) were performed before (Pre), immediately after (Post), and up to 10min after the endurance task. Endurance time, peak torque (PT) and electromyographic (EMG) activities of the biceps brachii and triceps brachii were recorded and analysed. Results showed that under Pre-test conditions, PT developed at 18:00h was higher than at 06:00h. No time-of-day effect appears for the endurance time and EMG activities during the test. No time-of-day effect was observed on either MVC or EMG recovery. From the results of this study, it seems that both muscle fatigue and recovery process are not time-of-day dependent. We conclude that circadian rhythm of the force do not influence the evaluation of muscle capacities during a submaximal exercise corresponding at 40% of MVC.

The effect of pedal rate and time of day on the time to exhaustion from high-intensity exercise

The aim of this study was to examine the supposed influence of pedal rate on the diurnal fluctuation of the time to exhaustion from high-intensity exercise. Eleven male cyclists performed three tests at 06:00 h and three at 18:00 h at a free pedal rate (FPR) and two imposed pedal rates (80% and 120% of the FPR). They performed the tests until exhaustion using a power output corresponding to 95% maximal power (Pmax). Time to exhaustion, rectal temperature, oxygen consumption (.VO2), M. quadriceps, vastus medialis, M. biceps femoris electromyographic Root Mean Square activity rise (RMS slope), and blood lactate concentration were measured. The mean time to exhaustion recorded at 18:00 h (270.6+/-104.8 sec) was greater than at 06:00 h (233.9+/-84.9 sec). The time to exhaustion was significantly greater when the pedal rate was imposed at 80% versus 120% FPR. The blood lactate concentration and absolute core temperature at the point of exhaustion were significantly higher during tests done at 18:00 h. There was no diurnal variation in core temperature increase, .VO2, and RMS slope. The time-of-day effect for every variable did not depend on pedal rate. Diurnal variations in maximal aerobic endurance cannot be explained by a change in aerobic metabolism or in muscular fatigue. The origin of the diurnal variation in the time to exhaustion is likely to lie in greater participation in anaerobic metabolism. Also, the influence of temperature on neuromuscular functioning as an explanation for the diurnal variation in performance cannot be excluded in this study. The hypothesis on the basis of which pedal rate would influence diurnal variations in time to exhaustion in cycling was not validated by this research.

Evaporative light scattering detection (ELSD): a tool for improved quality control of drug substances

Thanks to the recent technological advancements, evaporative light-scattering detection (ELSD) is regarded as a valuable alternative to UV detection for liquid chromatographic analysis of substances that do not contain a chromophore. In the field of substances for pharmaceutical use, LC-ELSD appears to be suitable for aminoglycosides, most of which (for ex. gentamicin) are presently controlled in the Ph. Eur. by pulsed amperometric detection. Other substances (ex sugars, triglycerides) presently employing refractometrric detection, could be conveniently analysed by LC-ELSD. ELS detection is regarded as robust and relatively simple, although not particularly sensitive. A key feature of ELSD is that - unlike refractometry - it can operate in gradient mode, thus allowing application of more selective liquid chromatographic methods. ELSD can also be used to set up MS-compatible methods, as the mobile phase constraints are essentially the same. Due to all the above, ELSD is becoming increasingly used in pharmacopoeial methods.

Limitation of cell adhesion by the elasticity of the extracellular matrix

Cell/matrix adhesions are modulated by cytoskeletal or external stresses and adapt to the mechanical properties of the extracellular matrix. We propose that this mechanosensitivity arises from the activation of a mechanosensor located within the adhesion itself. We show that this mechanism accounts for the observed directional growth of focal adhesions and the reduction or even cessation of their growth when cells adhere to a soft extracellular matrix. We predict quantitatively that both the elasticity and the thickness of the matrix play a key role in the dynamics of focal adhesions. Two different types of dynamics are expected depending on whether the thickness of the matrix is of order of or much larger than the adhesion size. In the latter situation, we predict that the adhesion region reaches a saturation size that can be tuned by the mechanical properties of the matrix.

Analysis of neomycin sulfate and framycetin sulfate by high-performance liquid chromatography using evaporative light scattering detection

A rapid and simple method for the determination of main components and related substances of both neomycin sulfate and framycetin sulfate by HPLC and evaporative light scattering detection (ELSD) is described. The method was also used to determine the neomycin B and the sample sulfate content. Detection and quantitation of aminoglycoside antibiotics are problematic because of the lack of UV absorbing chromophore. The use of a universal detector avoids the need for sample derivatization or use of specific detector based on pulsed amperometry described to be difficult in routine assays. Separation was performed with a Polaris C18 150 mm x 4.6 mm i.d., 3 microm reversed-phase column with a solution of 170mM trifluoroacetic acid (TFA) mobile phase at a flow rate of 0.2 mL/min. The chromatographic parameters were optimized with the help of experimental design software. Mass spectrometry (MS) was employed to confirm the ELSD profile. The final method was validated using methodology described by the International Conference of Harmonization in the field of Active Pharmaceutical Ingredients. Commercial samples of different sources were analyzed and results were in good agreement with specifications of the European Pharmacopoeia.

[Monoclonal immunoglobulin: national external quality assessment and diagnostic reasoning]

In 2003, for the scheme of the French national external quality assessment, Afssaps sent to medical laboratories a sample for which two analyses could be carried out: the electrophoresis of proteins and the characterization for monoclonal immunoglobulin. The purpose of this new approach was to make it possible to the laboratories to transpose their usual diagnostic reasoning. This survey recalled to the biologists that it is necessary to check the sensitivity of the test of electrophoresis of proteins used in first intention and to use advisedly the anti-serums anti-free chains. Moreover this operation reinforced the educational aspect of the external quality assessment, pointing out the importance to ensure the coherence of the results of these two analyses carried out with a same diagnostic aim.

Cell mechanosensitivity controls the anisotropy of focal adhesions

Cellular adhesions are modulated by cytoskeletal forces or external stresses and adapt to the mechanical properties of the extracellular matrix. We propose that this mechanosensitivity can be driven at least in part by the elastic, cell-contractility-induced deformations of protein molecules that form the adhesion. The model accounts for observations of anisotropic growth and shrinkage of focal adhesions in the direction of the force and predicts that focal adhesions only grow within a range of force that is determined by the composition and matrix properties. This prediction is consistent with the observations of a force threshold for the appearance of elongated focal adhesions and the disruption of adhesions into fibrils on a mobile extracellular matrix. The growth dynamics is calculated and the predicted sliding of focal adhesions is consistent with several experiments.

Increased cell size and Akt activation in HER-2/neu-overexpressing invasive ductal carcinoma of the breast

AIMS

To determine whether cell size is related to HER-2/neu status and/or to Akt activation in breast carcinomas. HER-2/neu overexpression is observed in 20-30% of invasive breast carcinomas with poor pronostic features, but little is known about the cell phenotype associated with HER-2/neu activation. Akt has been found to be involved in the HER-2/neu signal transduction pathway and Akt activation has been associated with increased cell size in various models.

METHODS AND RESULTS

A case-control study of invasive ductal carcinoma of the breast was carried out, including 21 cases displaying HER-2/neu overexpression and 20 HER-2/neu negative controls. Cytoplasmic and nuclear sizes were measured on digitized histological pictures using cell image analysis software. Akt expression analysis was performed by immunohistochemistry on formalin-fixed histological sections using an anti-phosphorylated-Akt (Ser473) antibody.

RESULTS

HER-2/neu-overexpressing carcinomas had a mean nuclear size of 75 +/- 22.2 micro m(2) and a mean cytoplasmic size of 187 +/- 52.3 micro m(2). Both values were higher than the nuclear and cytoplasmic size of HER-2/neu-negative cases (nucleus = 58 +/- 24.5 micro m(2), cytoplasm = 133 +/- 56.6 micro m(2); P = 0.02 and P =0.003, respectively). Up to 75% of the tumours with a cell size over 140 micro m(2) were HER-2/neu-positive. Immunohistochemical Akt expression was observed in 19/40 (47.5%) cases. The immunoreactivity was localized in the cytoplasm in eight cases, on the cell membrane in four cases and at both sites in seven cases. One case was not interpretable. Comparison between HER-2/neu and Akt status showed that Akt was detectable at the cell membrane in 43% (9/21) of HER-2/neu-positive and in 10% (2/19) of HER-2/neu-negative cases (P = 0.02).

CONCLUSIONS

HER-2/neu overexpression was consistently associated with increased cell size in invasive ductal carcinoma of the breast. This increase may be related to concomitant Akt activation. The assessment of activated pathways in HER-2/neu-overexpressing breast carcinomas may provide useful information for optimized individual HER-2/neu-targeted therapy.

Elastic deformations of grafted layers with surface stress

We calculate the elastic response of thin films grafted to a solid substrate whose upper surface is subject to a stress. This issue is addressed in the context of biological cell adhesion where adhesive junctions consist of a thin layer of proteins grafted to the extracellular matrix and sheared by the cell contractility apparatus. We show that the finite thickness of the layer limits stress-induced deformations to short ranges proportional to the thickness of the film. In addition, we show that the attachment boundary condition creates an effective shear response to surface stresses that couples all the directions, even for fluidlike layers. We predict that perturbations with wavelengths of order of the film thickness induce resonancelike responses for isotropic rubberlike materials or anisotropic media with high shear moduli. We use these results to predict the elastic deformations of a layer of proteins under shear stress and propose that the resulting, polarized elastic response to local surface forces can explain the observed, anisotropic growth of cell-substrate junctions when subject to external stresses.

Determination of gentamicin sulfate and related compounds by high-performance liquid chromatography with evaporative light scattering detection

A rapid and simple method for the separation and quantitation of gentamicin sulfate by HPLC coupled with evaporative light scattering detection (ELSD) has been developed. Detection of the different components of gentamicin is problematic because of the lack of UV absorbing chromophore. The use of the universal ELSD avoids the need for sample derivatization or use of specific detector such as pulsed amperometry. Separation was performed on a highpurity C18 125 mm x 4 mm i.d., 3 microm, reversed phase column with 48.5 mM trifluoroacetic acid-methanol (97:3, v/v), as mobile phase at a flow rate of 0.7 ml/min. The influence of the gas nature, gas pressure and temperature of the drift tube of the detector on the detection response was investigated. Optimization was performed with the help of a specific experimental design software. This method allows the determination of the composition in components C1, C1a, C2, C2a and C2b of gentamicin sulfate samples. Mass spectrometry was employed to confirm the ELSD chromatographic profile. The method was validated using methodology described by the International Conference of Harmonization in the field of Medicinal Substances. Commercial samples of different sources were analyzed and results were in good agreement with specifications of both European and United States Pharmacopoeia.

GermOnline, a cross-species community knowledgebase on germ cell differentiation

GermOnline provides information and microarray expression data for genes involved in mitosis and meiosis, gamete formation and germ line development across species. The database has been developed, and is being curated and updated, by life scientists in cooperation with bioinformaticists. Information is contributed through an online form using free text, images and the controlled vocabulary developed by the GeneOntology Consortium. Authors provide up to three references in support of their contribution. The database is governed by an international board of scientists to ensure a standardized data format and the highest quality of GermOnline's information content. Release 2.0 provides exclusive access to microarray expression data from Saccharomyces cerevisiae and Rattus norvegicus, as well as curated information on approximately 700 genes from various organisms. The locus report pages include links to external databases that contain relevant annotation, microarray expression and proteome data. Conversely, the Saccharomyces Genome Database (SGD), S.cerevisiae GeneDB and Swiss-Prot link to the budding yeast section of GermOnline from their respective locus pages. GermOnline, a fully operational prototype subject-oriented knowledgebase designed for community annotation and array data visualization, is accessible at http://www.germonline.org. The target audience includes researchers who work on mitotic cell division, meiosis, gametogenesis, germ line development, human reproductive health and comparative genomics.

Interlaboratory study of a liquid chromatography method for erythromycin: determination of uncertainty

Erythromycin is a mixture of macrolide antibiotics produced by Saccharopolyspora erythreas during fermentation. A new method for the analysis of erythromycin by liquid chromatography has previously been developed. It makes use of an Astec C18 polymeric column. After validation in one laboratory, the method was now validated in an interlaboratory study. Validation studies are commonly used to test the fitness of the analytical method prior to its use for routine quality testing. The data derived in the interlaboratory study can be used to make an uncertainty statement as well. The relationship between validation and uncertainty statement is not clear for many analysts and there is a need to show how the existing data, derived during validation, can be used in practice. Eight laboratories participated in this interlaboratory study. The set-up allowed the determination of the repeatability variance, s(2)r and the between-laboratory variance, s(2)L. Combination of s(2)r and s(2)L results in the reproducibility variance s(2)R. It has been shown how these data can be used in future by a single laboratory that wants to make an uncertainty statement concerning the same analysis.

Polymers grafted to a fluid and flexible membrane: extreme sensitivity to the grafting density

Equilibrium phase coexistence between two chemical species implies the equality of the chemical potentials and of the osmotic pressures. We study this problem on a deformable membrane when one type of the molecules serves as anchor for polymeric chains immersed in the surrounding medium (considered as a good solvent). We derive the general conditions for phase coexistence when both the curvature of the membrane and the density field of the anchor molecule are free to adjust themselves. We show that curvature favors phase segregation. Our model predicts that membranes decorated with polymeric chains exhibit new shape bifurcations without equivalent in fixed density systems.

[Human infertility: meiotic genes as potential candidates]

Up to now, the identification of gene mutations causing infertility in humans remains poorly investigated. Temporal progression through meiosis and meiosis specific genes had been extensively characterized in yeast. Recently some mammalian homologous were found. The molecular mechanisms regulating entry into and progression through meiosis in mammals are still unknown. However, disruption of some meiotic genes in mouse showed an essential role of them in meiotic chromosome synapsis and gametogenesis. Moreover, the phenotype of gonads in null mutant mice for some meiotic genes (failure to initiate or blockage in meiosis, lack of gametes or small size of gonads...) could be strikingly similar to clinical observations found in human infertility. The aim of this study was to identify putative mutations in 5 meiotic genes of several clinically well-characterized patients who present unexplained infertility (normal karyotype, women with premature ovarian failure, men with azospermia and without Y micro-deletion). For this purpose, the exons of these 5 genes (DMC1, SPO11, MSH4, MSH5, CCNA1) were all amplified by PCR with specific primers and each amplified-exon was sequenced. Sequences were aligned in comparison to the human corresponding gene available in Genbank. Many heterozygous mutations were found in different genes. Two homozygous mutations were found in MSH4 and DMC1 genes in a young man presenting a testis vanishing syndrome and a woman presenting a premature ovarian failure, respectively. Consequences of such mutations will be examined and verified in model organisms (yeast, mouse) to check the relevance of the mutations in clinical setting.

The binding site of acetylcholine receptor as visualized in the X-Ray structure of a complex between alpha-bungarotoxin and a mimotope peptide

We have determined the crystal structure at 1.8 A resolution of a complex of alpha-bungarotoxin with a high affinity 13-residue peptide that is homologous to the binding region of the alpha subunit of acetylcholine receptor. The peptide fits snugly to the toxin and adopts a beta hairpin conformation. The structures of the bound peptide and the homologous loop of acetylcholine binding protein, a soluble analog of the extracellular domain of acetylcholine receptor, are remarkably similar. Their superposition indicates that the toxin wraps around the receptor binding site loop, and in addition, binds tightly at the interface of two of the receptor subunits where it inserts a finger into the ligand binding site, thus blocking access to the acetylcholine binding site and explaining its strong antagonistic activity.

Histochemical method for characterization of enzyme crystals: application to crystals of Torpedo californica acetylcholinesterase

Histochemical methods are employed to detect and localize a wide range of enzymes. Even though protein crystallographers do not commonly use this technique, the extensively used colorimetric reaction of Karnovsky was successfully adapted for easy and quick identification of acetylcholinesterase crystals. The method relies on the reduction of ferricyanide to ferrocyanide by thiocholine, released from acetylthiocholine by enzymatic hydrolysis, followed by formation of a cupric ferrocyanide precipitate, and allows rapid differentiation between salt and enzyme crystals and between native and inhibited crystals of the enzyme.