Characterization of the D-allose-mediated regulation of sugar transport in Chinese hamster fibroblasts

Exposure to D-allose has been demonstrated to lead to decreased 2-deoxy-D-glucose (2-DG) and 3-0-methyl-D-glucose transport in the V79 Chinese hamster lung fibroblast cell line. The effect of D-allose 1) was maximal after 4 hours exposure to the cells; 2) was optimal between 2.77 and 5.55 mM D-allose; and 3) led to a decreased Vmax for 2-DG transport with no change in the transport Km value. The decrease in 2-DG transport induced by D-allose was reversible and the reversal was differentially affected by cycloheximide, being blocked by a low concentration of cycloheximide (0.05 micrograms/ml) but not a high concentration of the inhibitor (5 micrograms/ml). D-allose did not competitively inhibit the transport of 2-DG while D-glucose under similar conditions yielded a Kl for 2-DG transport inhibition of 1.7 mM. Additionally, D-allose did not affect the phosphorylation of 2-DG by hexokinase in cell-free cytosol. The data indicate that D-allose has significant lowering effects on sugar transport activity. Additionally, while the sugar itself may be the active component in sugar transport regulation, the effect is not blocked by inhibition of protein synthesis but the synthesis of a regulatory protein(s) may be involved in the return of sugar transport following D-allose removal.     

FECAL METHANOGENS AND VERTEBRATE EVOLUTION

It has been assumed that the feeding habits of vertebrates predispose the variety of intestinal differentiations and the composition of the microbial biota living in their intestinal tracts. Consequently, the presence of methanogenic bacteria in the various differentiations of the large intestine and the foregut of herbivorous vertebrates had been attributed primarily to the existence of anaerobic habitats and the availability of carbon dioxide and hydrogen originating from the fermentative microbial digestion of plant-based diets. However, Australian ratites, many murids, and several New World primates lack methanogens, despite their intestinal differentiations and their vegetarian feeding habits. Crocodiles, giant snakes, aardvarks, and ant-eaters on the other hand release significant amounts of methane. A determination of methane emissions by 253 vertebrate species confirmed that competence for intestinal methanogenic bacteria is shared by related species and higher taxa, irrespective of different feeding habits. In “methanogenic” branches of the evolutionary tree, a variety of differentiations of the large intestine evolved and, in some cases, differentiations of the foregut. In contrast, the lack of competence for methanogens in chiropterans/insectivores and carnivores apparently has precluded the evolution of specialized fermenting differentiations of the digestive tract. Our observations reveal that the presence of intestinal methanogenic bacteria is under phylogenetic rather than dietary control: competence for intestinal methanogenic bacteria is a plesiomorphic (primitive-shared) character among reptiles, birds, and mammals. This competence for methanogenic bacteria has been crucial for the evolution of the amniotes.     

N-glycosylation induced changes in tau protein dynamics reveal its role in tau misfolding and aggregation: A microsecond long molecular dynamics study

Various posttranslational modifications like hyperphosphorylation, O-GlcNAcylation, and acetylation have been attributed to induce the abnormal folding in tau protein. Recent in vitro studies revealed the possible involvement of N-glycosylation of tau protein in the abnormal folding and tau aggregation. Hence, in this study, we performed a microsecond long all atom molecular dynamics simulation to gain insights into the effects of N-glycosylation on Asn-359 residue which forms part of the microtubule binding region. Trajectory analysis of the stimulations coupled with essential dynamics and free energy landscape analysis suggested that tau, in its N-glycosylated form tends to exist in a largely folded conformation having high beta sheet propensity as compared to unmodified tau which exists in a large extended form with very less beta sheet propensity. Residue interaction network analysis of the lowest energy conformations further revealed that Phe378 and Lys353 are the functionally important residues in the peptide which helped in initiating the folding process and Phe378, Lys347, and Lys370 helped to maintain the stability of the protein in the folded state.     

Feeding the fairy shrimp Streptocephalus (Anostraca - Crustacea) with the rotifer Anuraeopsis

Laboratory-cultured Streptocephalus torvicornis were offered 8 concentrations (from 6 to 800 ind. ml^–1) of Anuraeopsis fissa for periods of 2 h 30 min. Two size classes, small (male: 14.7 mm± 1.6, female: 15.4 mm± 1.3) and large (male: 20.0 mm±2.0, female: 23.1 mm± 1.5), of S. torvicornis were used. Functional response for large S. torvicornis (both sexes) plateaued at 400 rotifers ml^–1, while in small specimens it did so at 200 prey ml^–1. Females consumed significantly more (30%) prey than males. Large males consumed maximum 4730 rotifers h^–1, females 6560 h^–1.     

Fluctuating temperatures have different effects on embryonic sensitivity to ABA in Sorghum varieties with contrasting pre-harvest sprouting susceptibility

The effect of fluctuating temperatures on the germination ofimmature caryopses of two Sorghum varieties presenting contrastingsusceptibility to pre-harvest sprouting was investigated. Fluctuatingtemperatures were able to stimulate germination of immaturecaryopses of both varieties from early stages of development(i.e. 15 d after pollination). Isolated embryos from both varietiesgerminated well in water irrespective of the thermal regimeof incubation. However, the ability of ABA to block germinationin Redland B2 (sproutingsusceptible) isolated embryos was significantlyreduced when embryos were incubated under fluctuating temperaturesfrom 23 DAP onwards. No such effect was found in IS 9530 (sprouting-resistant)embryos. No differences in the pattern with which embryonicABA content decreased during whole grain incubation were foundin 25 and 35 DAP grains from both varieties incubated underconstant or fluctuating temperatures. Therefore, these resultsindicate that alternating temperatures can promote germinationthrough different mechanisms. One of them is the decrease inembryo sensitivity to ABA inhibition which appears to be actingin Redland B2 caryopses from 23 DAP onwards; the other one seemsto be independent of ABA level and sensitivity and is activeat very early stages of development in one variety (RedlandB2) and throughout seed development in the other (IS 9530). Key words: Germination, dormancy, fluctuating temperatures, abscisic acid, seed development, Sorghum bicolor     

Structurally symmetrical,easily polarizable hydrogen bonds between side chains in proteins and proton-conducting mechanisms. III

(L -Cys)_n, (L -Lys)_n, and (L -Glu)_n were studied by ir spectroscopy in terms of their degree of deprotonation or protonation. It is shown that structurally symmetrical, easily polarizable SH ?S^? ? ^?S ?HS, N⁺H ?N ? N ?H⁺N, and OH ?O^? ? ^?O ?HO hydrogen bonds are formed between the side chains. The different wave number distributions of the ir continua caused by these hydrogen bonds show that the barrier in the double-minimum proton potential decreases in the series of these hydrogen bonds. The stability of these hydrogen bonds against hydration increases in this series. The OH ?O^? ? ^?O ?HO bonds are not broken by small amounts of water. With (L -Cys)_n the formation of easily polarizable hydrogen bonds and a β-structure–coil transition are strongly interdependent. As a result of this coupling effect, the β-structure–coil transition becomes cooperative. With (L -Glu)_n, the formation of the polarizable hydrogen bonds and the observed conformational change are independent processes. The (L -Glu)_n conformation changes from α-helix to coil only if more than 80% of the residues are deprotonated. Finally, on the basis of the various types of easily polarizable hydrogen bonds, charge shifts in active centers of enzymes and the proton-conducting mechanism through hydrophobic regions of biological membranes are discussed.     

Synthesis,Antimicrobial Activity and Molecular Docking Study of Novel α‐(Diphenylphosphoryl)‐ and α‐(Diphenylphosphorothioyl)cycloalkanone Oximes

A series of novel α‐(diphenylphosphoryl)‐ and α‐(diphenylphosphorothioyl)cycloalkanone oximes have been synthesized in search for novel bioactive molecules. Their structures were characterized by various spectroscopic methods including IR, NMR (¹H, ³¹P, ¹³C), mass spectrometry and single crystal X‐ray diffraction. The newly synthesized phosphorus‐containing oximes were screened for their in vitro antimicrobial activity against Gram‐positive bacteria (Staphylococcus aureus and Bacillus subtilis), Gram‐negative bacteria (Escherichia coli and Salmonella typhimurium) and fungal strains (Candida albicans and Candida glabrata). The biological assays showed that all the studied compounds exhibited high antibacterial and antifungal activities at only 0.1–2.1 μg/mL. In silico molecular docking studies in FabH enzyme active site were performed in order to predict the possible interaction modes and binding energies of the drug candidates at the molecular level.     

Does Serum 25-Hydroxyvitamin D Influence Muscle Development during Puberty in Girls? - A 7-Year Longitudinal Study

Vitamin D is well known for its regulatory role in calcium and phosphate homeostasis, but its role in muscle mass and strength during growth remains inconclusive. We explored the association of serum 25-hydroxyvitamin D (25(OH)D) with muscle development in girls from 11 to 18-years old. Whole body lean tissue mass (LM_WB), appendicular lean mass (aLM), muscle cross-sectional area at the lower leg (mCSA), maximal voluntary contraction of elbow flexors (MVC_elbow) and knee extensors (MVC_knee) were assessed in 217 girls aged 10–13 years (at baseline), 215 in 2-year and 226 in 7.5-year follow-up. Serum concentration of 25(OH)D and intact parathyroid hormone (PTH) were analyzed retrospectively and girls were categorized according to their 25(OH)D levels (consistently insufficient 25(OH)D G_LL <50 nmol/l and consistently sufficient G_HH >50 nmol/l from baseline to 7-year follow-up). We found that 25(OH)D level declined until menarche (p<0.05) while LM_WB, aLM, mCSA, MVC_elbow and MVC_knee continued to increase (p<0.001 for all) post menarche. At pre-menarche, the G_LL (n = 34) had higher LM_WB and aLM than the G_HH (n = 21, p<0.05), while post-menarche the G_HH (n = 15) had a greater catch-up gain in LM_WB (p = 0.004), aLM (p = 0.001) and mCSA (p = 0.027) compared to the G_LL (n = 65) over the first 2-year period. At the age of 18, no differences in muscle mass/strength between the low (n = 151) and high (n = 77) levels of 25(OH)D groups were found. This finding was independent of vitamin D receptor genotype and other confounders. In conclusion, our results showed that levels of 25(OH)D have no significant negative influence on the development of muscle mass and strength during pubertal growth both with longitudinal and cross-sectional comparison. On the contrary, our results suggest that the temporary negative association between 25(OH)D and muscle mass arises as a consequence of fast growth prior to menarche, and this negative association is diminished through catch-up growth after menarche.     

Tuning the Fano Resonance Between Localized and Propagating Surface Plasmon Resonances for Refractive Index Sensing Applications

Localized and propagating surface plasmon resonances are known to show very pronounced interactions if they are simultaneously excited in the same nanostructure. Here, we study the Fano interference that occurs between localized surface plasmon resonance (LSPR) and propagating surface plasmon polariton (SPP) modes by means of phase-sensitive spectroscopic ellipsometry. The sample structures consist of periodic gratings of gold nanodisks on top of a continuous gold layer and a thin dielectric spacer, in which the structural dimensions were tuned in such a way that the dipolar LSPR mode and the propagating SPP modes are excited in the same spectral region. We observe pronounced anti-crossing and strongly asymmetric line shapes when both modes move to each other’s vicinity, accompanied of largely increased phase differences between the respective plasmon resonances. Moreover, we show that the anti-crossing can be exploited to increase the refractive index sensitivity of the localized modes dramatically, which result in largely increased values for the figure-of-merit which reaches values between 24 and 58 for the respective plasmon modes.     

Structure of Protein Related to Dan and Cerberus: Insights into the Mechanism of Bone Morphogenetic Protein Antagonism

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