Experimental characterization and constitutive modeling of the biomechanical behavior of male human urethral tissues validated by histological observations.

This work aims at observing the mechanical behavior of the membranous and spongy portions of urethrae sampled on male cadavers in compliance with French regulations on postmortem testing, in accordance with the Scientific Council of body donation center of Grenoble. In this perspective, a thermostatic water tank was designed to conduct ex vivo planar tension tests in a physiological environment, i.e., in a saline solution at a temperature of [Formula: see text] [Formula: see text]. In order to observe the anisotropy of the tissues, the samples were tested in two directions. Tests consisting of a series of load-unload cycles of increasing amplitudes were performed to highlight their viscous behavior. The results were then discussed according to the microstructure of tissue, which was investigated using different staining methods and histological analysis. The observed behaviors were then fitted using an anisotropic hyperelastic or a visco-hyperelastic matrix-fiber model.

Horizontal drying fronts in films of colloidal dispersions: influence of hydrostatic pressure and collective diffusion.

The origin and time evolution of heterogeneities in drying colloidal films is still a matter of debate. In this work, we studied the behaviour of horizontal drying fronts in a 1D configuration. The effects of hydrostatic pressure and collective diffusion of charged particles, neglected so far, were introduced. We made use of the new simulation tool based on cellular automata we recently presented (Langmuir 2015 & 2017). To check the simulation results, measurements of film profiles in the wet state and drying front velocities were performed with silica colloids. It was shown that taking hydrostatic pressure into account much improves agreement between theory and experiment. On the other hand, the simulation showed that collective diffusion slows down the drying fronts, even more when the Debye length is increased. This latter effect remains to be checked experimentally. This work opens the way to further improvements of theory and simulation, notably 2D and 3D simulations.

A new tribological experimental setup to study confined and sheared monolayers.

We have developed an original experimental setup, coupling tribology, and velocimetry experiments together with a direct visualization of the contact. The significant interest of the setup is to measure simultaneously the apparent friction coefficient and the velocity of confined layers down to molecular scale. The major challenge of this experimental coupling is to catch information on a nanometer-thick sheared zone confined between a rigid spherical indenter of millimetric radius sliding on a flat surface at constant speed. In order to demonstrate the accuracy of this setup to investigate nanometer-scale sliding layers, we studied a model lipid monolayer deposited on glass slides. It shows that our experimental setup will, therefore, help to highlight the hydrodynamic of such sheared confined layers in lubrication, biolubrication, or friction on solid polymer.

Mechanical behaviour׳s evolution of a PLA-b-PEG-b-PLA triblock copolymer during hydrolytic degradation.

PLA-b-PEG-b-PLA is a biodegradable triblock copolymer that presents both the mechanical properties of PLA and the hydrophilicity of PEG. In this paper, physical and mechanical properties of PLA-b-PEG-b-PLA are studied during in vitro degradation. The degradation process leads to a mass loss, a decrease of number average molecular weight and an increase of dispersity index. Mechanical experiments are made in a specific experimental set-up designed to create an environment close to in vivo conditions. The viscoelastic behaviour of the material is studied during the degradation. Finally, the mechanical behaviour is modelled with a linear viscoelastic model. A degradation variable is defined and included in the model to describe the hydrolytic degradation. This variable is linked to physical parameters of the macromolecular polymer network. The model allows us to describe weak deformations but become less accurate for larger deformations. The abilities and limits of the model are discussed.

The embalming of John of Lancaster, first Duke of Bedford (1435 AD): A forensic analysis.

During the Middle Ages and Renaissance, embalming the cadaver of the elite was common practice, being a highly technical treatment mixing vegetal and mineral substances. To assess the exact kind of embalming reserved for the dead body (with the practical necessities of desiccation and good odour), we performed a full biomedical analysis of the mummified remains of John Plantagenet of Lancaster, first Duke of Bedford, regent of France for his nephew, the English King Henri VI (died 1435 AD). Here, we show, among other aspects, that the body was embalmed using substances whose origins were in apothecary and botany: mercury, myrtle, mint, frankincense, lime and, possibly, cinnamon and copper.

An original architectured NiTi silicone rubber structure for biomedical applications.

This paper deals with composite structures for biomedical applications. For this purpose, an architectured tubular structure composed of Nickel Titanium (NiTi) Shape Memory Alloy (SMA) and silicone rubber was fabricated. One of the main interests of such structures is to ensure a good adhesion between its two constitutive materials. A previous study of the authors (Rey et al., 2014) has shown that the adhesion between NiTi and silicone rubber can be improved by an adhesion promoter or plasma treatment. However, adhesion promoters are often not biocompatible. Hence, plasma treatment is favored to be used in the present study. Three different gases were tested; air, argon and oxygen. The effects of these treatments on the maximum force required to pull-out a NiTi wire from the silicone rubber matrix were investigated by means of pull-out tests carried out with a self-developed device. Among the three gases, a higher maximum force was obtained for argon gas in the plasma treatment. A tube shaped architectured NiTi/silicone rubber structure was then produced using this treatment. The composite was tested by means of a bulge test. Results open a new way of investigations for architectured NiTi-silicone structures for biomechanical applications.

Upscaling the diffusion equations in particulate media made of highly conductive particles. I. Theoretical aspects.

Many analytical and numerical works have been devoted to the prediction of macroscopic effective transport properties in particulate media. Usually, structure and properties of macroscopic balance and constitutive equations are stated a priori. In this paper, the upscaling of the transient diffusion equations in concentrated particulate media with possible particle-particle interfacial barriers, highly conductive particles, poorly conductive matrix, and temperature-dependent physical properties is revisited using the homogenization method based on multiple scale asymptotic expansions. This method uses no a priori assumptions on the physics at the macroscale. For the considered physics and microstructures and depending on the order of magnitude of dimensionless Biot and Fourier numbers, it is shown that some situations cannot be homogenized. For other situations, three different macroscopic models are identified, depending on the quality of particle-particle contacts. They are one-phase media, following the standard heat equation and Fourier's law. Calculations of the effective conductivity tensor and heat capacity are proved to be uncoupled. Linear and steady state continuous localization problems must be solved on representative elementary volumes to compute the effective conductivity tensors for the two first models. For the third model, i.e., for highly resistive contacts, the localization problem becomes simpler and discrete whatever the shape of particles. In paper II [Vassal, Phys. Rev. E 77, 011303 (2008)], diffusion through networks of slender, wavy, entangled, and oriented fibers is considered. Discrete localization problems can then be obtained for all models, as well as semianalytical or fully analytical expressions of the corresponding effective conductivity tensors.

Upscaling the diffusion equations in particulate media made of highly conductive particles. II. Application to fibrous materials.

In paper I [Vassal, Phys. Rev. E77, 011302 (2008)] of this contribution, the effective diffusion properties of particulate media with highly conductive particles and particle-particle interfacial barriers have been investigated with the homogenization method with multiple scale asymptotic expansions. Three different macroscopic models have been proposed depending on the quality of contacts between particles. However, depending on the nature and the geometry of particles contained in representative elementary volumes of the considered media, localization problems to be solved to compute the effective conductivity of the two first models can rapidly become cumbersome, time and memory consuming. In this second paper, the above problem is simplified and applied to networks made of slender, wavy and entangled fibers. For these types of media, discrete formulations of localization problems for all macroscopic models can be obtained leading to very efficient numerical calculations. Semianalytical expressions of the effective conductivity tensors are also proposed under simplifying assumptions. The case of straight monodisperse and homogeneously distributed slender fibers with a circular cross section is further explored. Compact semianalytical and analytical estimations are obtained when fiber-fiber contacts are perfect or very poor. Moreover, two discrete element codes have been developed and used to solve localization problems on representative elementary volumes for the same types of contacts. Numerical results underline the significant roles of the fiber content, the orientation of fibers as well as the relative position and orientation of contacting fibers on the effective conductivity tensors. Semianalytical and analytical predictions are discussed and compared with numerical results.

Molecular cloning reveals that the p160 Myb-binding protein is a novel, predominantly nucleolar protein which may play a role in transactivation by Myb.

We have previously detected two related murine nuclear proteins, p160 and p67, that can bind to the leucine zipper motif within the negative regulatory domain of the Myb transcription factor. We now describe the molecular cloning of cDNA corresponding to murine p160. The P160 gene is located on mouse chromosome 11, and related sequences are found on chromosomes 1 and 12. The predicted p160 protein is novel, and in agreement with previous studies, we find that the corresponding 4.5-kb mRNA is ubiquitously expressed. We showed that p67 is an N-terminal fragment of p160 which is generated by proteolytic cleavage in certain cell types. The protein encoded by the cloned p160 cDNA and an engineered protein (p67*) comprising the amino-terminal region of p160 exhibit binding specificities for the Myb and Jun leucine zipper regions identical to those of endogenous p160 and p67, respectively. This implies that the Myb-binding site of p160 lies within the N-terminal 580 residues and that the Jun-binding site is C-terminal to this position. Moreover, we show that p67* but not p160 can inhibit transactivation by Myb. Unexpectedly, immunofluorescence studies show that p160 is localized predominantly in the nucleolus. The implications of these results for possible functions of p160 are discussed.

[Evaluation protocol of cochlear implants in children under 5 years of age]. / Protocole d'évaluation de l'implant cochléaire chez l'enfant de moins de 5 ans.

Special tests are necessary to assess the cochlear implant efficacy on a prelingually deaf child implanted before age 5 y. We propose to quantify comportment, comprehension, auditory perception and expression as percentage of a same age normally hearing child's scores. The particular items are detailed.

Detection of proteins that bind to the leucine zipper motif of c-Myb.

The product of the c-myb proto-oncogene, c-Myb, binds DNA and can enhance transcription of genes bearing copies of the DNA sequence it recognises. Deletion or disruption of a negative regulatory domain (NRD) in the carboxyl portion of c-Myb results in enhanced transactivating capacity and in parallel, leads to activation of its ability to transform haemopoietic cells. Since mutational analysis has shown that one critical element within the NRD is a leucine zipper motif, we have sought to identify cellular proteins that can interact with the c-Myb leucine zipper. Using fusion proteins containing this region as an affinity reagent, we have identified two nuclear proteins, p67 and p160, that bind to the wild-type, but not to a mutated c-Myb leucine zipper. These two proteins were shown to be related by comparison of peptides generated by partial digestion. While p160 was found to be ubiquitous amongst different murine haemopoietic cell lines, and was also present in NIH3T3 fibroblasts, p67 was detected in a restricted set of immature myeloid cells. Intriguingly p160, but not p67, could also bind to the c-Jun leucine zipper.

Negative autoregulation of c-Myb activity by homodimer formation through the leucine zipper.

The trans-activating and transforming capacities of the c-myb proto-oncogene product (c-Myb) are negatively regulated through a leucine zipper structure in its negative regulatory domain. We show here tht in cotransfection assays, maximal Myb-induced trans-activation occurs with relatively low amounts of wild-type c-Myb, while higher levels of c-Myb result in reduced Myb-induced trans-activation. By contrast, this apparent negative autoregulation is not observed with a c-Myb mutant containing an impaired leucine zipper. Data presented here suggest that this negative autoregulation of trans-activation by wild-type c-Myb is a consequence of homodimer formation by c-Myb through its leucine zipper and of the inability of c-Myb dimers to bind DNA. These findings point to a novel mechanism of regulation of a transcription factor.

Action of cysteaminylphenols on human melanoma cells in vivo and in vitro: 4-S-cysteaminylphenol binds protein disulphide isomerase.

Systemically administered 4-S-cysteaminylphenol (4-S-CAP) and N-acetyl-4-S-CAP inhibited the growth of xenografts of a human melanoma cell line but not of an ovarian tumour cell line. No selective cytotoxicity for melanoma cells was observed in culture, however. Further study of the in vitro mechanism of 4-S-CAP toxicity showed minimal inhibition of tyrosinase activity or DNA, RNA and protein synthesis, and there was no phase-specific arrest of the cell cycle. However, expression of an 80 kD melanosomal antigen was decreased. Cytotoxicity of 4-S-CAP in culture was decreased by simultaneous treatment with a monoamine oxidase inhibitor. An affinity column prepared from 4-S-CAP retained several proteins from a melanoma cell lysate. One protein, found also in HeLa cells, was identified by N-terminal sequencing as protein disulphide isomerase, a molecule which has multiple roles in the modification of secretory proteins. These results identify a protein target for 4-S-CAP as one possible mechanism of cytotoxicity.

Relationships between resistance to cross-linking agents and glutathione metabolism, aldehyde dehydrogenase isozymes and adenovirus replication in human tumour cell lines.

In a panel of 10 human tumour cell lines with no prior exposure to drugs in vitro, resistance to cisplatin correlated with resistance to the nitrogen mustard derivatives Asta Z-7557 (mafosfamide, an activated form of cyclophosphamide), melphalan and chlorambucil. Simultaneous treatment with DL-buthionine-S,R-sulfoximine did not enhance the toxicity of cisplatin or Asta Z-7557, and no correlation was found between drug resistance and cellular levels of metallothioneins (as judged by sensitivity to cadmium chloride), glutathione (GSH), GSH reductase, GSH transferase, or gamma-glutamyltranspeptidase. The two cell lines most resistant to Asta Z-7557 expressed aldehyde dehydrogenase cytosolic isozyme 1, found also in normal ovary, but not isozyme 3. Treatment of resistant cells with cisplatin or Asta Z-7557 inhibited cellular DNA synthesis and replication of adenovirus 5 to a lesser extent than in sensitive cells. The virus could be directly inactivated by both drugs prior to infection, subsequent replication being inhibited to the same extent in sensitive and resistant cells. In contrast to Asta Z-7557 and other DNA damaging agents, cisplatin was much more toxic to adenovirus (D37 0.022-0.048 microM) than to cells (D37 0.25-2.5 microM). The adenovirus 5 mutant Ad5ts125 having a G----A substitution was even more sensitive to cisplatin (D37 7-8 nM) than wild type virus and another mutant. Cisplatin was detoxified less by sonicated resistant resistant cells than sensitive cells, as judged by inactivation of Ad5ts125 added to the reaction mixture. It can be inferred that (i) the major differences in cellular resistance to cisplatin and Asta Z-7557 in the present material did not involve enhanced DNA repair or protection by metallothioneins or GSH, but were associated with the ability to continue cellular and viral DNA synthesis during treatment, (ii) resistance was not associated with less template damage, and (iii) the adenovirus genome may be a suitable probe for predicting tumour resistance to cisplatin and for elucidating the DNA sequence dependence of cisplatin toxicity.

Complementary expression of melanosomal antigens and constant expression of pigment-independent antigen during the evolution of melanocytic tumours.

We have generated monoclonal antibodies (MoAbs) against melanosomal proteins (MoAb 1C11 and MoAb HMSA-1) and a cytoplasmic protein strongly synthesized in neoplastic melanocytes but not associated with melanogenesis (MoAb 7H11). An immunohistochemical study of paraffin sections showed that nearly 90% of epidermal neoplastic melanocytes, including melanomas, expressed 1C11 antigen, whereas this antigen was poorly preserved in dermal melanocytic cells except melanomas. HMSA-1 antigen was expressed in a complementary manner to 1C11 antigen, being found in dermal naevus cells but not generally in the epidermal regions, except for dysplastic naevi and melanomas. In contrast, 7H11 antigen was distributed in nearly 90% of melanocytic tumours except solar lentigo and lentigo maligna lesions. The failure of MoAb 1C11 to react with dermal melanocytes may reflect a subtle alteration in melanogenesis during tumour evolution. Overall, the combined use of MoAbs serves as an accurate diagnosis of melanocytic tumours, the pigment-independent MoAb 7H11 being particularly useful for amelanotic and metastatic lesions.

Sensitivity of human melanoma cells to L-dopa and DL-buthionine (S,R)-sulfoximine.

Four of seven human melanoma cell lines were sensitive to killing by L-dopa (D37 1.0-4.7 microM) compared with fibroblasts, Hela, and three ovarian tumor cell lines (D37 12-59 microM). All seven melanoma lines, however, were sensitive to DL-buthionine(S,R)sulfoximine (BSO) (D37 0.73-8.5 microM) compared with the nonmelanoma cells (D37 25-68 microM). The melanoma line most sensitive to BSO (MM418) was highly melanized, proliferated slowly and was resistant to other agents [dopa, 5-(3-methyl-1-triazeno)5-imidazole-4-carboxamide, melphalan, methotrexate, hydroxyurea, etoposide, Adriamycin]. In most cell lines, L-dopa and BSO blocked cell proliferation in all phases of the cell cycle. Cellular sensitivity to dopa or BSO did not correlate with levels of total soluble SH, glutathione (GSH), GSH reductase, GSH peroxidase or GSH transferase, or with the extent of GSH depletion induced by the drug. No GSH transferase activity could be detected in the dopa-resistant HeLa line, indicating that detoxification of quinones is not an important mechanism of resistance. Within the group of melanoma cell lines, sensitivity to dopa correlated with decreased level of gamma-glutamyl transpeptidase (r = 0.81). However, the gamma-glutamyl transpeptidase inhibitor azaserine was less effective than BSO in enhancing the toxicity of dopa. It can be inferred that (a) there is no simple relationship between GSH metabolism and sensitivity to dopa or BSO in human melanoma cells, and (b) BSO may be an effective agent for melanoma.