Metabolic machinery encrypted in the Raman spectrum of influenza A virus-inoculated mammalian cells

Raman spectroscopy was applied with a high spectral resolution to a structural study of Influenza (type A) virus before and after its inoculation into Madin–Darby canine kidney cells. This study exploits the fact that the major virus and cell constituents, namely DNA/RNA, lipid, and protein molecules, exhibit peculiar fingerprints in the Raman spectrum, which clearly differed between cells and viruses, as well as before and after virus inoculation into cells. These vibrational features, which allowed us to discuss viral assembly, membrane lipid evolution, and nucleoprotein interactions of the virus with the host cells, reflected the ability of the virus to alter host cells’ pathways to enhance its replication efficiency. Upon comparing Raman signals from the host cells before and after virus inoculation, we were also able to discuss in detail cell metabolic reactions against the presence of the virus in terms of compositional variations of lipid species, the formation of fatty acids, dephosphorylation of high-energy adenosine triphosphate molecules, and enzymatic hydrolysis of the hemagglutinin glycoprotein.     

Adipose Tissue Lipolysis Promotes Exercise-induced Cardiac Hypertrophy Involving the Lipokine C16:1n7-Palmitoleate

Endurance exercise training induces substantial adaptive cardiac modifications such as left ventricular hypertrophy (LVH). Simultaneously to the development of LVH, adipose tissue (AT) lipolysis becomes elevated upon endurance training to cope with enhanced energy demands. In this study, we investigated the impact of adipose tissue lipolysis on the development of exercise-induced cardiac hypertrophy. Mice deficient for adipose triglyceride lipase (Atgl) in AT (atATGL-KO) were challenged with chronic treadmill running. Exercise-induced AT lipolytic activity was significantly reduced in atATGL-KO mice accompanied by the absence of a plasma fatty acid (FA) increase. These processes were directly associated with a prominent attenuation of myocardial FA uptake in atATGL-KO and a significant reduction of the cardiac hypertrophic response to exercise. FA serum profiling revealed palmitoleic acid (C16:1n7) as a new molecular co-mediator of exercise-induced cardiac hypertrophy by inducing nonproliferative cardiomyocyte growth. In parallel, serum FA analysis and echocardiography were performed in 25 endurance athletes. In consonance, the serum C16:1n7 palmitoleate level exhibited a significantly positive correlation with diastolic interventricular septum thickness in those athletes. No correlation existed between linoleic acid (18:2n6) and diastolic interventricular septum thickness. Collectively, our data provide the first evidence that adipose tissue lipolysis directly promotes the development of exercise-induced cardiac hypertrophy involving the lipokine C16:1n7 palmitoleate as a molecular co-mediator. The identification of a lipokine involved in physiological cardiac growth may help to develop future lipid-based therapies for pathological LVH or heart failure.     

A New Critical Conformational Determinant of Multidrug Efflux by an MFS Transporter

Secondary multidrug (Mdr) transporters utilize ion concentration gradients to actively remove antibiotics and other toxic compounds from cells. The model Mdr transporter MdfA from Escherichia coli exchanges dissimilar drugs for protons. The transporter should open at the cytoplasmic side to enable access of drugs into the Mdr recognition pocket. Here we show that the cytoplasmic rim around the Mdr recognition pocket represents a previously overlooked important regulatory determinant in MdfA. We demonstrate that increasing the positive charge of the electrically asymmetric rim dramatically inhibits MdfA activity and sometimes even leads to influx of planar, positively charged compounds, resulting in drug sensitivity. Our results suggest that unlike the mutants with the electrically modified rim, the membrane-embedded wild-type MdfA exhibits a significant probability of an inward-closed conformation, which is further increased by drug binding. Since MdfA binds drugs from its inward-facing environment, these results are intriguing and raise the possibility that the transporter has a sensitive, drug-induced conformational switch, which favors an inward-closed state.     

The Ancient Origins of Neural Substrates for Land Walking

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Peptidergic innervation of leg muscles of the cockroach,Periplaneta americana (L.), and a possible role in modulation of muscle contraction

FMRFamide-related peptides of insects are particularly important because of their possible function as neurohormones and neuromodulators on a wide variety of tissues. Part of this study was an investigation of the immunofluorescent staining of motor nerves which arise in the metathoracic ganglion, examined in wholemount using an antiserum that recognizes extended -RFamide peptides (generally recognized to be of the FMRFamide family). This antiserum revealed immunochemical staining of numerous cell bodies in the metathoracic ganglion and of axons in peripheral nerve 5, a large nerve which contains both motor and sensory fibres. Axons staining positive for FMRFamide-related peptides were traced in nerve 5 as far as the femur-tibia joint, and into the first (sensory-motor) and third (motor only) ramus of nerve 5. Reverse-phase HPLC with radioimmunoassay revealed a peak of FMRFamide-related peptide activity in nerve 5 that was coincident with a peak found when thoracic ganglia were processed in the same fashion. A physiological assay was devised to test the ability of various non-native peptides to alter the characteristics of contraction of skeletal muscles of the legs. Using neurally evoked contractions of coxal depressor muscles of the metathoracic leg it was determined that several non-native peptides could potentiate muscle contractions.The results of this study suggest that muscles of the legs receive innervation by identifiable, FMRFamide-related peptide-containing neurons and that the release of peptide(s) at the muscle may be yet another method of modulating the mechanics of muscle contraction.Abbreviations D _f fast depressor motor neuron - D _s slow depressor motor neuron - DU M dorsal unpaired median - FaRPs FMRFamide related peptides - FEFe fast extensor of the femur - FFFe fast flexor of the femur - FITC fluorescein isothiocyanate - FPC fast promotor of the coxa - FPT fast flexor of the pretarsus - I _1–3 inhibitory motor neurons - LMS leucomyosuppressin, N5 nerve 5 - N5r1 first ramus of nerve 5 - PBS phosphate buffered saline - PLCl posterior lateral cluster - RIA radioimmunoassay - SETi slow extensor of the tibia - SFTi slow flexor of the tibia - TFA trifluoroacetic acid - VMCl ventral median cluster     

Social selection parapatry in Afrotropical sunbirds

The extent of range overlap of incipient and recent species depends on the type and magnitude of phenotypic divergence that separates them, and the consequences of phenotypic divergence on their interactions. Signal divergence by social selection likely initiates many speciation events, but may yield niche‐conserved lineages predisposed to limit each others’ ranges via ecological competition. Here, we examine this neglected aspect of social selection speciation theory in relation to the discovery of a nonecotonal species border between sunbirds. We find that Nectarinia moreaui and Nectarinia fuelleborni meet in a ～6 km wide contact zone, as estimated by molecular cline analysis. These species exploit similar bioclimatic niches, but sing highly divergent learned songs, consistent with divergence by social selection. Cline analyses suggest that within‐species stabilizing social selection on song‐learning predispositions maintains species differences in song despite both hybridization and cultural transmission. We conclude that ecological competition between moreaui and fuelleborni contributes to the stabilization of the species border, but that ecological competition acts in conjunction with reproductive interference. The evolutionary maintenance of learned song differences in a hybrid zone recommend this study system for future studies on the mechanisms of learned song divergence and its role in speciation.     

Comparison of <Emphasis Type="Italic">Chlorella vulgaris</Emphasis> and cyanobacterial biomass: cultivation in urban wastewater and methane production

Anaerobic digestion of microalgae is hampered by its complex cell wall. Against this background, cyanobacteria cell walls render this biomass as an ideal substrate for overcoming this drawback. The aim of the present study was to compare the growth of two cyanobacteria (Aphanizomenon ovalisporum and Anabaena planctonica) and a microalga (Chlorella vulgaris) in urban wastewater when varying the temperature (22, 27 and 32 °C). Cyanobacterial optimal growth for both strains was attained at 22 °C, while C. vulgaris did not show remarkable differences among temperatures. For all the microorganisms, ammonium removal was higher than phosphate. Biomass collected was subjected to anaerobic digestion. Methane yield of C. vulgaris was 184.8 mL CH₄ g COD in^?1 while with A. ovalisporum and A. planctonica the methane production was 1.2- and 1.4-fold higher. This study showed that cyanobacteria growth rates could be comparable to microalgae while presenting the additional benefit of an increased anaerobic digestibility.     

Regulation of H2a-specific proteolysis by the histone H3:H4 tetramer

We have studied the limited cleavage of H2a in the H2a:H2b histone dimer by the H2a-specific protease under physiological conditions (neutral pH, 0.1 M NaCl) using a variety of histone-DNA reconstitutes as substrates and/or regulators of the partially purified enzyme. Under these conditions the protease cleaves H2a in "native" dimer-DNA reconstitutes but not in "native" octamer-DNA reconstitutes. Treatment of the enzyme with saturating amounts of H3:H4 tetramer-DNA prior to addition of dimer-DNA substrate results in complete inhibition of H2a-specific proteolysis. Sucrose gradient sedimentation experiments indicate that the protease binds reversibly to tetramer-DNA and that this leads to the reversible inhibition of enzymatic activity. Using three different tetramer-DNA complexes, we found native tetramer-DNA to be a more effective inhibitor than either trypsin-treated tetramer-DNA or acetylated tetramer-DNA. We conclude that under physiological conditions, the H2a-specific protease binds primarily to the highly basic amino-terminal domain of the H3:H4 tetramer, and this binding lowers the effective concentration of enzyme available to cleave H2a. Although no cleaved H2a is produced when protease is mixed with native octamer-DNA, incubation of the enzyme with acetylated octamer-DNA results in H2a-specific proteolysis. This is the first demonstration that the H2a-specific protease activity can be modulated by a physiologically relevant process (e.g. histone acetylation). We propose that the sequestered protease may be functionally regulated in vivo through reversible post-translational modifications to the NH2-terminal domains of the histone H3:H4 tetramer.