A computational algorithm to simulate disorganization of collagen network in injured articular cartilage

Cartilage defects are a known risk factor for osteoarthritis. Estimation of structural changes in these defects could help us to identify high risk defects and thus to identify patients that are susceptible for the onset and progression of osteoarthritis. Here, we present an algorithm combined with computational modeling to simulate the disorganization of collagen fibril network in injured cartilage. Several potential triggers for collagen disorganization were tested in the algorithm following the assumption that disorganization is dependent on the mechanical stimulus of the tissue. We found that tensile tissue stimulus alone was unable to preserve collagen architecture in intact cartilage as collagen network reoriented throughout the cartilage thickness. However, when collagen reorientation was based on both tensile tissue stimulus and tensile collagen fibril strains or stresses, the collagen network architecture was preserved in intact cartilage. Using the same approach, substantial collagen reorientation was predicted locally near the cartilage defect and particularly at the cartilage–bone interface. The developed algorithm was able to predict similar structural findings reported in the literature that are associated with experimentally observed remodeling in articular cartilage. The proposed algorithm, if further validated, could help to predict structural changes in articular cartilage following post-traumatic injury potentially advancing to impaired cartilage function.     

Downregulation of connexin40 and increased prevalence of atrial arrhythmias in transgenic mice with cardiac-restricted overexpression of tumor necrosis factor

Atrial arrhythmias, primarily atrial fibrillation, have been independently associated with structural remodeling and with inflammation. We hypothesized that sustained inflammatory signaling by tumor necrosis factor (TNF) would lead to alterations both in underlying atrial myocardial structure and in atrial electrical conduction. We performed ECG recording, intracardiac electrophysiology studies, epicardial mapping, and connexin immunohistochemical analyses on transgenic mice with targeted overexpression of TNF in the cardiac compartment (MHCsTNF) and on wild-type (WT) control mice (age 8-16 wk). Atrial and ventricular conduction abnormalities were always evident on ECG in MHCsTNF mice, including a shortened atrioventricular interval with a wide QRS duration secondary to junctional rhythm. Supraventricular arrhythmias were observed in five of eight MHCsTNF mice, whereas none of the mice demonstrated ventricular arrhythmias. No arrhythmias were observed in WT mice. Left ventricular conduction velocity during apical pacing was similar between the two mouse groups. Connexin40 was significantly downregulated in MHCsTNF mice. In contrast, connexin43 density was not significantly altered in MHCsTNF mice, but rather dispersed away from the intercalated disks. In conclusion, sustained inflammatory signaling contributed to atrial structural remodeling and downregulation of connexin40 that was associated with an increased prevalence of atrial arrhythmias.     

Inhibition of Personally-Relevant Angry Faces Moderates the Effect of Empathy on Interpersonal Functioning

While empathy is typically assumed to promote effective social interactions, it can sometimes be detrimental when it is unrestrained and overgeneralized. The present study explored whether cognitive inhibition would moderate the effect of empathy on social functioning. Eighty healthy young adults underwent two assessments six months apart. Participants’ ability to suppress interference from distracting emotional stimuli was assessed using a Negative Affective Priming Task that included both generic and personally-relevant (i.e., participants’ intimate partners) facial expressions of emotion. The UCLA Life Stress Interview and Empathy Quotient were administered to measure interpersonal functioning and empathy respectively. Multilevel modeling demonstrated that higher empathy was associated with worse concurrent interpersonal outcomes for individuals who showed weak inhibition of the personally-relevant depictions of anger. The effect of empathy on social functioning might be dependent on individuals’ ability to suppress interference from meaningful emotional distractors in their environment.     

Directed evolution of an endoinulinase from Talaromyces purpureogenus toward efficient production of inulooligosaccharides

Inulinases are fructofuranosyl hydrolases that target the β‐2,1 linkage of inulin and hydrolyze it into fructose, glucose and inulooligosaccharides (IOS), the latter are of growing interest as dietary fibers. Inulinases from various microorganisms have been purified, characterized and produced for industrial applications. However, there remains a need for inulinases with increased catalytic activity and better production yields to improve the hydrolysis process and fulfill the growing industrial demands for specific fibers. In this study, we used directed enzyme evolution to increase the yield and activity of an endoinulinase enzyme originated from the filamentous fungus Talaromyces purpureogenus (Penicillium purpureogenum ATCC4713). Our directed evolution approach yielded variants showing up to fivefold improvements in soluble enzyme production compared to the starting point which enabled high‐yield production of highly purified recombinant enzyme. The distribution of the enzymatic reaction products demonstrated that after 24 h of incubation, the main product (57%) had a degree of polymerization of 3 (DP3). To the best of our knowledge, this is the first application of directed enzyme evolution to improve inulooligosaccharide production. The approach enabled the screening of large genetic libraries within short time frames and facilitated screening for improved enzymatic activities and properties, such as substrate specificity, product range, thermostability and pH optimum. © 2018 American Institute of Chemical Engineers Biotechnol. Prog., 34:868–877, 2018     

Scrutiny of electrochemically-driven electrocatalysis of C-19 steroid 1α-hydroxylase (CYP260A1) from Sorangium cellulosum So ce56

Direct electrochemistry and bioelectrocatalysis of a newly discovered C-19 steroid 1α-hydroxylase (CYP260A1) from the myxobacterium Sorangium cellulosum So ce56 were investigated. CYP260A1 was immobilized on screen-printed graphite electrodes (SPE) modified with gold nanoparticles, stabilized by didodecyldimethylammonium bromide (SPE/DDAB/Au). Cyclic voltammograms in argon-saturated substrate free 0.1 M potassium phosphate buffer, pH 7.4, and in enzyme-substrate complex with androstenedione demonstrated a redox processes with a single redox couple of E^0′ of −299 ± 16 mV and −297.5 ± 21 mV (vs. Ag/AgCl), respectively. CYP260A1 exhibited an electrocatalytic activity detected by an increase of the reduction current in the presence of dissolved oxygen and upon addition of the substrate (androstenedione) in the air-saturated buffer. The catalytic current of the enzyme correlated with substrate concentration in the electrochemical system and this dependence can be described by electrochemical Michaelis-Menten model. The products of CYP260A1-depended electrolysis at controlled working electrode potential of androstenedione were analyzed by mass-spectrometry. MS analysis revealed a mono-hydroxylated product of CYP260A1-dependent electrocatalytic reaction towards androstenedione.     

XPO1 Inhibition Preferentially Disrupts the 3D Nuclear Organization of Telomeres in Tumor Cells

Previous work has shown that the three‐dimensional (3D) nuclear organization of telomeres is altered in cancer cells and the degree of alterations coincides with aggressiveness of disease. Nuclear pores are essential for spatial genome organization and gene regulation and XPO1 (exportin 1/CRM1) is the key nuclear export protein. The Selective Inhibitor of Nuclear Export (SINE) compounds developed by Karyopharm Therapeutics (KPT‐185, KPT‐330/selinexor, and KPT‐8602) inhibit XPO1 nuclear export function. In this study, we investigated whether XPO1 inhibition has downstream effects on the 3D nuclear organization of the genome. This was assessed by measuring the 3D telomeric architecture of normal and tumor cells in vitro and ex vivo. Our data demonstrate for the first time a rapid and preferential disruption of the 3D nuclear organization of telomeres in tumor cell lines and in primary cells ex vivo derived from treatment‐naïve newly diagnosed multiple myeloma patients. Normal primary cells in culture as well as healthy lymphocyte control cells from the same patients were minimally affected. Using both lymphoid and non‐lymphoid tumor cell lines, we found that the downstream effects on the 3D nuclear telomere structure are independent of tumor type. We conclude that the 3D nuclear organization of telomeres is a sensitive indicator of cellular response when treated with XPO1 inhibitors. J. Cell. Physiol. 231: 2711–2719, 2016. © 2016 The Authors. Journal of Cellular Physiology published by Wiley Periodicals, Inc.     

Effect of temperature and parasite density on three species ofAphytis (Hymenoptera: Aphelinidae), parasitising California red scale

Summary Three species ofAphytis parasites of California red scale,Aonidiella aurantii (Maskell) were each confined at different densities with approximately equal numbers of scale insects at several constant temperatures to determine the effect of these factors on progeny production and distribution and the search rate. Egg location on the host body by the parasites was unaffected by temperature or parasite density.A. melinus laid its eggs both dorsally and ventrally in equal proportions whileA. lingnanensis andA. chrysomphali laid their eggs ventrally. Progeny production byA. melinus andA. lingnanensis increased at the higher temperature; that ofA. chrysomphali did not. Unlike the other species,A. chrysomphali failed to oviposit at 32°C. Although increasing parasite density reduced progeny production in bothA. melinus andA. lingnanensis, they were able to maintain an almonst constant search rate. This was due to their ability to distribute their eggs among the hosts more regularly at the higher parasite densities. While the mechanism of this process is easy to understand forA. melinus which behaved as a gregarious parasite, it is unclear forA. lingnanensis, which is almost a solitary parasite. The progeny production and the search rate ofA. chrysomphali dropped significantly with increasing parasite density.     

Functional response to host density by the egg parasiteTrichogramma pretiosum

The effect of host density on parasitism byTrichogramma pretiosum Riley was studied by exposing groups of 150, 300, 600 or 1200 eggs of potato tuber moth to 2, 4 or 8 female parasites per group. The parasite exhibited a type 2 functional response. As host density increasedT. pretiosum parasitised more hosts, but at a decreasing rate. The attack coefficient (a′) decreased as parasite density increased, whereas the handling time (T _h ) remained almost constant. The search rate (a) decreased with increasing host density.T. pretiosum responded to increasing host density by increasing the number of its encounters with hosts and the number of hosts it parasitised only up to host density of 300 when the parasite density was 2 and up to host density of 600 when the parasite densities were greater and then remained almost constant. The observed incidence of parasitism was higher than that expected on the assumption that the parasites behaved the same at higher host densities as at the lowest. When parasite density was raised from 2 to 8 females per group the percentage of female progeny fell from about 73 to about 48%. A 2-fold increase in the number of female progeny was observed when parasite density was reduced from 8 to 2 and also when the host density was raised from 150 to 1200 eggs.     

Hyphal growth ofHypomyces chlorinus Tul.: An autoradiographic study

Summary The incorporation of the chitin precursor N-acetyl-D-(1-³H) glucosamine byH. chlorinus has been studied by light and electron microscopic autoradiography. Light microscopic autoradiography showed that the incorporation occured preferentially at the hyphal apex. Autoradiograms from electron microscopy were quantitatively evaluated to determine the relative radioactivity incorporation between the cell wall and cytoplasm: this showed that (³H) incorporation took place mainly in the plasmalemma-wall complex. However a small amount of N-acetyl glucosamine can enter into the cytoplasmic space and is then transported by endomembranes (Golgi apparatus-vesicles) to the plasmalemma-cell wall interface before polymerization.Abbreviations PATAg Periodic acid-thiocarbohydrazide-silver proteinate - PTA phosphotungstic acid