Pressure induced ageing of polymers

The nonlinearly viscoelastic response of an amorphous homopolymer is considered under aspects of time dependent free volume behavior. In contrast to linearly viscoelastic solids, this model couples shear and volume deformation through a shift function which influences the rate of molecular relaxation or creep. Sample computations produce all those qualitative features one observes normally in uniaxial tension including the rate dependent formation of a yield point as a consequence of the history of an imposed pressure

Supplementation of Aspergillus glaucus with gfdB gene encoding a glycerol 3-phosphate dehydrogenase in Aspergillus nidulans

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GABAB receptor-mediated activation of astrocytes by gamma-hydroxybutyric acid

The gamma-aminobutyric acid (GABA) metabolite gamma-hydroxybutyric acid (GHB) shows a variety of behavioural effects when administered to animals and humans, including reward/addiction properties and absence seizures. At the cellular level, these actions of GHB are mediated by activation of neuronal GABAB receptors (GABABRs) where it acts as a weak agonist. Because astrocytes respond to endogenous and exogenously applied GABA by activation of both GABAA and GABABRs, here we investigated the action of GHB on astrocytes on the ventral tegmental area (VTA) and the ventrobasal (VB) thalamic nucleus, two brain areas involved in the reward and proepileptic action of GHB, respectively, and compared it with that of the potent GABABR agonist baclofen. We found that GHB and baclofen elicited dose-dependent (ED50: 1.6 mM and 1.3 µM, respectively) transient increases in intracellular Ca2+ in VTA and VB astrocytes of young mice and rats, which were accounted for by activation of their GABABRs and mediated by Ca2+ release from intracellular store release. In contrast, prolonged GHB and baclofen exposure caused a reduction in spontaneous astrocyte activity and glutamate release from VTA astrocytes. These findings have key (patho)physiological implications for our understanding of the addictive and proepileptic actions of GHB

The Viscoelastic Properties of Passive Eye Muscle in Primates. II: Testing the Quasi-Linear Theory

We have extensively investigated the mechanical properties of passive eye muscles, in vivo, in anesthetized and paralyzed monkeys. The complexity inherent in rheological measurements makes it desirable to present the results in terms of a mathematical model. Because Fung's quasi-linear viscoelastic (QLV) model has been particularly successful in capturing the viscoelastic properties of passive biological tissues, here we analyze this dataset within the framework of Fung's theory

The Viscoelastic Properties of Passive Eye Muscle in Primates. I: Static Forces and Step Responses

The viscoelastic properties of passive eye muscles are prime determinants of the deficits observed following eye muscle paralysis, the root cause of several types of strabismus. Our limited knowledge about such properties is hindering the ability of eye plant models to assist in formulating a patient's diagnosis and prognosis. To investigate these properties we conducted an extensive in vivo study of the mechanics of passive eye muscles in deeply anesthetized and paralyzed monkeys. We describe here the static length-tension relationship and the transient forces elicited by small step-like elongations. We found that the static force increases nonlinearly with length, as previously shown. As expected, an elongation step induces a fast rise in force, followed by a prolonged decay. The time course of the decay is however considerably more complex than previously thought, indicating the presence of several relaxation processes, with time constants ranging from 1 ms to at least 40 s. The mechanical properties of passive eye muscles are thus similar to those of many other biological passive tissues. Eye plant models, which for lack of data had to rely on (erroneous) assumptions, will have to be updated to incorporate these properties

On the origin of proteins in human drusen : the meet, greet and stick hypothesis

This research was part-supported by de Algemene Nederlandse Vereniging ter Voorkoming van Blindheid (ANVVB), de Stichting Blinden-Penning, de Gelderse Blinden Stichting, de Landelijke Stichting voor Blinden en Slechtzienden (LSBS), Stichting Oogfonds Nederland, Stichting MD Fonds and Stichting Retina Nederland Fonds (represented by Uitzicht, grants 2011-6 and 2014-7 to A.A.B.), de Rotterdamse Stichting Blindenbelangen (RSB), de Haagse Stichting Blindenhulp, Stichting Lijf en Leven, Stichting voor Ooglijders (to A.A.B.); ZonMW grant nr 446001002 (to A.A.B. and C.K.); the Bill Brown Charitable Trust, Moorfields Eye Hospital Special Trustees, Mercer Fund from Fight for Sight, the Eye-Risk project funded by the European Union’s Horizon 2020 research and innovation programme under grant agreement No 634479 (I.L. and E.E.), Fight for Sight project grant (I.L. and A.S.), the Bright Focus Foundation grant nr M2015370 (to SMH).Retinal drusen formation is not only a clinical hallmark for the development of age-related macular degeneration (AMD) but also for other disorders, such as Alzheimer's disease and renal diseases. The initiation and growth of drusen is poorly understood. Attention has focused on lipids and minerals, but relatively little is known about the origin of drusen-associated proteins and how they are retained in the space between the basal lamina of the retinal pigment epithelium and the inner collagenous layer space (sub-RPE-BL space). While some authors suggested that drusen proteins are mainly derived from cellular debris from processed photoreceptor outer segments and the RPE, others suggest a choroidal cell or blood origin. Here, we reviewed and supplement the existing literature on the molecular composition of the retina/choroid complex, to gain a more complete understanding of the sources of proteins in drusen. These “drusenomics” studies showed that a considerable proportion of currently identified drusen proteins is uniquely originating from the blood. A smaller, but still large fraction of drusen proteins comes from both blood and/or RPE. Only a small proportion of drusen proteins is uniquely derived from the photoreceptors or choroid. We next evaluated how drusen components may “meet, greet and stick” to each other and/or to structures like hydroxyapatite spherules to form macroscopic deposits in the sub-RPE-BL space. Finally, we discuss implications of our findings with respect to the previously proposed homology between drusenogenesis in AMD and plaque formation in atherosclerosis.PostprintPeer reviewe

Long-Distance Translocation of Protein during Morphogenesis of the Fruiting Body in the Filamentous Fungus, Agaricus bisporus

Commercial cultivation of the mushroom fungus, Agaricus bisporus, utilizes a substrate consisting of a lower layer of compost and upper layer of peat. Typically, the two layers are seeded with individual mycelial inoculants representing a single genotype of A. bisporus. Studies aimed at examining the potential of this fungal species as a heterologous protein expression system have revealed unexpected contributions of the mycelial inoculants in the morphogenesis of the fruiting body. These contributions were elucidated using a dual-inoculant method whereby the two layers were differientially inoculated with transgenic β-glucuronidase (GUS) and wild-type (WT) lines. Surprisingly, use of a transgenic GUS line in the lower substrate and a WT line in the upper substrate yielded fruiting bodies expressing GUS activity while lacking the GUS transgene. Results of PCR and RT-PCR analyses for the GUS transgene and RNA transcript, respectively, suggested translocation of the GUS protein from the transgenic mycelium colonizing the lower layer into the fruiting body that developed exclusively from WT mycelium colonizing the upper layer. Effective translocation of the GUS protein depended on the use of a transgenic line in the lower layer in which the GUS gene was controlled by a vegetative mycelium-active promoter (laccase 2 and β-actin), rather than a fruiting body-active promoter (hydrophobin A). GUS-expressing fruiting bodies lacking the GUS gene had a bonafide WT genotype, confirmed by the absence of stably inherited GUS and hygromycin phosphotransferase selectable marker activities in their derived basidiospores and mycelial tissue cultures. Differientially inoculating the two substrate layers with individual lines carrying the GUS gene controlled by different tissue-preferred promoters resulted in up to a ∼3.5-fold increase in GUS activity over that obtained with a single inoculant. Our findings support the existence of a previously undescribed phenomenon of long-distance protein translocation in A. bisporus that has potential application in recombinant protein expression and biotechnological approaches for crop improvement

Research Update on Extreme-Mass-Ratio Inspirals

The inspirals of stellar-mass mass compact objects into massive black holes in the centres of galaxies are one of the most important sources of gravitational radiation for space-based detectors like LISA or eLISA. These extreme-mass-ratio inspirals (EMRIs) will enable an ambitious research program with implications for astrophysics, cosmology, and fundamental physics. This article is a summary of the talks delivered at the plenary session on EMRIs at the 10th International LISA Symposium. It contains research updates on the following topics: astrophysics of EMRIs; EMRI science potential; and EMRI modeling.Comment: 17 pages, no figures. Proceedings of the LISA Symposium X, to be published at the Journal of Physic

In vitro phosphorylation as tool for modification of silk and keratin fibrous materials

An overview is given of the recent work on in vitro enzymatic phosphorylation of silk fibroin and human hair keratin. Opposing to many chemical "conventional" approaches, enzymatic phosphorylation is in fact a mild reaction and the treatment falls within "green chemistry" approach. Silk and keratin are not phosphorylated in vivo, but in vitro. This enzyme-driven modification is a major technological breakthrough. Harsh chemical chemicals are avoided, and mild conditions make enzymatic phosphorylation a real "green chemistry" approach. The current communication presents a novel approach stating that enzyme phosphorylation may be used as a tool to modify the surface charge of biocompatible materials such as keratin and silk