RESUMO
Recent findings on the similarity between electron and positronium scattering at the same velocity [Brawley et al., Science 330, 789 (2010)] have guided us towards the realization of a detectable flux of positronium atoms at beam energies five times lower than previously obtained, enabling total cross sections to be measured in the energy range â¼(1-7) eV for the first time. In collision with Ar and Xe, the total cross sections of positronium are found to be smallest at the lowest energy probed, approaching those of the Ramsauer-Townsend minima for electron projectiles. Additional structure has been observed in the case of positronium scattering at incident energies around 5 eV.
RESUMO
The first absolute experimental determinations of the differential cross sections for the formation of ground-state positronium are presented for He, Ar, H2, and CO2 near 0°. Results are compared with available theories. The ratio of the differential and integrated cross sections for the targets exposes the higher propensity for forward emission of positronium formed from He and H2.
RESUMO
Paenibacillus sp. EJP73 has been previously demonstrated as a mycorrhization helper bacterium (MHB) for the Lactarius rufus-Pinus sylvestris symbiosis in both laboratory and glasshouse experiments. In the present study, the effect of Paenibacillus sp. EJP73 metabolites on L. rufus EO3 pre-symbiotic growth was tested in two agar plate-based systems. Specifically, volatile metabolites were investigated using a dual plate system, in which the presence of strain EJP73 resulted in a significant negative effect on L. rufus EO3 hyphal radial growth but enhanced hyphal branching and reduced internode distance. Soluble metabolites produced by strain EJP73 were tested on L. rufus EO3 growth in single-agar plate assays by incorporating bacterial cell-free whole or molecular weight fraction spent broth into the agar. Whole spent broth had a negative effect on hyphal growth, whereas a low molecular weight fraction (100-1,000) promoted colony radial growth. Headspace and spent broth analysis of strain EJP73 cultures revealed 2,5-diisopropylpyrazine to be the most significant component. Synthesised 2,5-diisopropylpyrazine and elevated CO2 (2,000 ppm) were tested as specific volatile metabolites in the dual plate system, but neither produced the response shown when strain EJP73 was present. Increased pre-symbiotic hyphal branching leading to increased likelihood of plant infection may be an important MHB mechanism for strain EJP73. Although the precise signal molecules could not be identified, the work suggests a number of metabolites may work synergistically to increase L. rufus root colonisation.
Assuntos
Basidiomycota/crescimento & desenvolvimento , Fatores Biológicos/metabolismo , Hifas/crescimento & desenvolvimento , Micorrizas/crescimento & desenvolvimento , Paenibacillus/metabolismo , Pinus sylvestris/microbiologia , Compostos Orgânicos Voláteis/metabolismo , Basidiomycota/efeitos dos fármacos , Fatores Biológicos/química , Fatores Biológicos/farmacologia , Hifas/efeitos dos fármacos , Peso Molecular , Micorrizas/efeitos dos fármacos , Paenibacillus/química , Raízes de Plantas/microbiologia , Compostos Orgânicos Voláteis/farmacologiaRESUMO
The total cross sections of positronium (Ps) scattering from a carbon-dioxide molecule have been measured over the range (7-400) eV incident-Ps energy. For the first time in Ps collisions, a resonantlike structure is observed. For the present target, it occurs around 9.5 eV followed by a broader peak at â¼60 eV. Following Brawley et al. [Science 330, 789 (2010)] who have observed similarities between the total cross sections of positronium and of electrons incident upon a given target at the same velocity, a corresponding comparison is made for CO2. The comparison suggests that the former peak corresponds to the well-known 2Π(u) shape resonance which occurs for electrons at an incident velocity of 0.5 a.u. Further features are discussed and theoretical input is sought.
RESUMO
By following the intracellular processing of recycling transferrin receptors and the selective sorting of a-2 macroglobulin in chick embryo fibroblasts, we have shown that the concentration of 60 nm diam tubules which surrounds the centrioles represents a distal compartment on the recycling pathway. In migrating cells transferrin receptor tracers can be loaded into this compartment and then chased to the cell surface. When they emerge the recycling transferrin receptors are distributed over the surface of the leading lamella.
Assuntos
Compartimento Celular , Movimento Celular/fisiologia , Fibroblastos/fisiologia , Receptores da Transferrina/metabolismo , alfa-Macroglobulinas/metabolismo , Animais , Transporte Biológico , Membrana Celular/metabolismo , Células Cultivadas , Centríolos/metabolismo , Embrião de Galinha , Membranas Intracelulares/metabolismo , Lisossomos/fisiologia , Microscopia de Fluorescência , Microscopia Imunoeletrônica , Receptores da Transferrina/isolamento & purificação , Transferrina/isolamento & purificação , Transferrina/metabolismoRESUMO
The transcytotic pathway followed by the polymeric IgA receptor (pIgR) carrying its bound ligand (dIgA) from the basolateral to the apical surface of polarized MDCK cells has been mapped using morphological tracers. At 20 degreesC dIgA-pIgR internalize to interconnected groups of vacuoles and tubules that comprise the endosomal compartment and in which they codistribute with internalized transferrin receptors (TR) and epidermal growth factor receptors (EGFR). Upon transfer to 37 degreesC the endosome vacuoles develop long tubules that give rise to a distinctive population of 100-nm-diam cup-shaped vesicles containing pIgR. At the same time, the endosome gives rise to multivesicular endosomes (MVB) enriched in EGFR and to 60-nm-diam basolateral vesicles. The cup-shaped vesicles carry the dIgA/pIgR complexes to the apical surface where they exocytose. Using video microscopy and correlative electron microscopy to study cells grown thin and flat we show that endosome vacuoles tubulate in response to dIgA/pIgR but that the tubules contain TR as well as pIgR. However, we show that TR are removed from these dIgA-induced tubules via clathrin-coated buds and, as a result, the cup-shaped vesicles to which the tubules give rise become enriched in dIgA/pIgR. Taken together with the published information available on pIgR trafficking signals, our observations suggest that the steady-state concentrations of TR and unoccupied pIgR on the basolateral surface of polarized MDCK cells are maintained by a signal-dependent, clathrin-based sorting mechanism that operates along the length of the transcytotic pathway. We propose that the differential sorting of occupied receptors within the MDCK endosome is achieved by this clathrin-based mechanism continuously retrieving receptors like TR from the pathways that deliver pIgR to the apical surface and EGFR to the lysosome.
Assuntos
Polaridade Celular/fisiologia , Endocitose , Receptores ErbB/metabolismo , Proteínas de Membrana/metabolismo , Receptores Fc/metabolismo , Receptores da Transferrina/metabolismo , Animais , Linhagem Celular , Membrana Celular/fisiologia , Membrana Celular/ultraestrutura , Cães , Endossomos/fisiologia , Endossomos/ultraestrutura , Imunoglobulina A/metabolismo , Rim , Cinética , Microscopia Eletrônica , Microscopia de VídeoRESUMO
Quantum physics is undoubtedly the most successful theory of the microscopic world, yet the complexities which arise in applying it even to simple atomic and molecular systems render the description of basic collision probabilities a formidable task. For this reason, approximations are often employed, the validity of which may be restricted to given energy regimes and/or targets and/or projectiles. Now we have found that the lognormal function, widely used for the probability distribution of macroscopic stochastic events (as diverse as periods of incubation of and recovery from diseases, size of grains, abundance of species, fluctuations in economic quantities, etc.) may also be employed to describe the energy dependence of inelastic collisions at the quantum level (including ionization, electron capture and excitation by electrons, positrons, protons, antiprotons, etc.), by allowing for the relevant threshold energy. A physical interpretation is discussed in this article by analogy with the heat capacity of few-level systems in solid state physics. We find the generality of the analysis to extend also to nuclear reactions. As well as aiding the description of collision probabilities for quantum systems, this finding is expected to impact also on the fundamental understanding of the interface between the classical and quantum domains.
RESUMO
Dipicolinic acid (DPA) is a distinctive biomarker for bacterial spores. Here, we present the successful demonstration of dramatic Switch-OFF sensing of DPA using an easily synthesised Eu(iii) phosphor applied primarily in light-emitting devices. The sensor in the presence of water and phosphate is also demonstrated to be effective.
RESUMO
[reaction: see text] Intramolecular 5-exo cyclization of 3-(2-methyleneaziridin-1-yl)propyl radicals leads to the generation of a highly strained, bicyclic aziridinylcarbinyl radical that undergoes C-N bond fission to the ring-expanded aminyl radical. This methodology provides access to substituted 3-methylenepiperidines and, by combining it with an additional 5-exo-trig cyclization reaction, the octahydroindolizidine skeleton.
RESUMO
(S)-Coniine is made using a reaction which assembles the piperidine ring by the sequential formation of four new chemical bonds and installs the C-2 stereogenic centre with high levels of diastereocontrol (90% de).
Assuntos
Alcaloides/síntese química , Aziridinas/química , Piperidinas/síntese química , Estrutura Molecular , Piperidinas/química , Plantas/química , EstereoisomerismoRESUMO
Lithiation and alkylation of a 2-isopropylidineaziridine bearing an (S)-alpha-methylbenzyl group on nitrogen proceeds with high levels of diastereocontrol (80-90% de).
RESUMO
Identification of genes contributing to mouse seizure susceptibility can reveal novel genes or pathways that provide insight into human epilepsy. Using mouse chromosome substitution strains and interval-specific congenic strains (ISCS), we previously identified an interval conferring pilocarpine-induced limbic seizure susceptibility on distal mouse chromosome 10 (Ch10). We narrowed the region by generating subcongenics with smaller A/J Ch10 segments on a C57BL/6J (B6) background and tested them with pilocarpine. We also tested pilocarpine-susceptible congenics for 6-Hz ECT (electroconvulsive threshold), another model of limbic seizure susceptibility, to determine whether the susceptibility locus might have a broad effect on neuronal hyperexcitability across more than one mode of limbic seizure induction. The ISCS Line 1, which contained the distal 2.7 Mb segment from A/J (starting at rs29382217), was more susceptible to both pilocarpine and ECT. Line 2, which was a subcongenic of Line 1 (starting at rs13480828), was not susceptible, thus defining a 1.0 Mb critical region that was unique to Line 1. Bioinformatic approaches identified 45 human orthologs within the unique Line 1 susceptibility region, the majority syntenic to human Ch12. Applying an epilepsy network analysis of known and suspected excitability genes and examination of interstrain genomic and brain expression differences revealed novel candidates within the region. These include Stat2, which plays a role in hippocampal GABA receptor expression after status epilepticus, and novel candidates Pan2, Cdk2, Gls2 and Cs, which are involved in neural cell differentiation, cellular remodeling and embryonic development. Our strategy may facilitate discovery of novel human epilepsy genes.
Assuntos
Cromossomos de Mamíferos/genética , Loci Gênicos , Predisposição Genética para Doença , Convulsões/genética , Animais , Mapeamento Cromossômico , Cromossomos Humanos Par 12/genética , Biologia Computacional , Humanos , Camundongos , Camundongos Congênicos , Camundongos Endogâmicos C57BL , Pilocarpina/toxicidade , Convulsões/induzido quimicamente , Convulsões/fisiopatologiaAssuntos
Acidentes de Trânsito , Condução de Veículo , Hospitalização , Adolescente , Adulto , Idoso , Humanos , Tempo de Internação , Pessoa de Meia-Idade , Nova Escócia , Ferimentos e LesõesAssuntos
Atitude , Meio Ambiente , Universidades , Feminino , Humanos , Masculino , Inquéritos e QuestionáriosRESUMO
We report on a patient with a low testosterone level which occurred during treatment with venlafaxine. The testosterone level increased when the medication was discontinued. Possible clinical correlation with amelioration of paraphilia is discussed.
Assuntos
Cicloexanóis/efeitos adversos , Inibidores Seletivos de Recaptação de Serotonina/efeitos adversos , Testosterona/análise , Adulto , Cicloexanóis/administração & dosagem , Transtorno Depressivo/tratamento farmacológico , Humanos , Masculino , Inibidores Seletivos de Recaptação de Serotonina/administração & dosagem , Cloridrato de VenlafaxinaRESUMO
Complexes of cell-surface receptors and their ligands are commonly internalized by endocytosis and enter a prelysosomal endosomal pathway for further processing. Fluorescence microscopy and video recording of living cells to trace the passage of ligand-receptor complexes has identified the endosomal compartment as an extensive network of tubular cisternae. Endocytosed material entering this reticulum enters discrete swellings, identified as multivesicular bodies by electron microscopy, which move along the reticulum towards the pericentriolar area.
Assuntos
Endocitose , Receptores ErbB/metabolismo , Receptores da Transferrina/metabolismo , Transporte Biológico , Linhagem Celular , Membrana Celular/metabolismo , Membrana Celular/ultraestrutura , Receptores ErbB/ultraestrutura , Humanos , Microscopia Eletrônica , Microscopia de Fluorescência , Receptores da Transferrina/ultraestruturaRESUMO
A series of compounds related to the left-hand domain of the azinomycins have been made and evaluated for cytotoxic activity against a small panel of human tumour cell lines. The epoxide ring is shown to be essential for biological activity. Cytotoxicity is also shown to be sensitive to changes in the substitution pattern on the aromatic ring and the amide group.
Assuntos
Antibacterianos/síntese química , Antineoplásicos/síntese química , Compostos Bicíclicos Heterocíclicos com Pontes/química , Glicopeptídeos , Antibacterianos/farmacologia , Antineoplásicos/farmacologia , Compostos Azabicíclicos , Dipeptídeos , Ensaios de Seleção de Medicamentos Antitumorais , Humanos , Peptídeos e Proteínas de Sinalização Intercelular , Naftalenos , Peptídeos , Células Tumorais CultivadasRESUMO
Gold conjugates have been used to quantitate human transferrin receptors (hTfnRs) on transfected chick embryo fibroblasts. No relationship could be found between the number of hTfnRs and the number of clathrin-coated pits. However, hTfnRs are also associated with flat clathrin lattices that lie outside invaginated pits. With increasing levels of receptor expression, the density of hTfnRs within flat lattices increases, and at the highest levels of expression the total area of flat lattice increases up to 3-fold. These results show that increased receptor numbers can promote clathrin lattice growth and suggest that the recruitment of receptors like hTfnRs is an essential step in lattice construction. We conclude that the process of invagination, which gives rise to coated pits, is regulated separately.
Assuntos
Clatrina/fisiologia , Invaginações Revestidas da Membrana Celular/fisiologia , Receptores da Transferrina/fisiologia , Animais , Membrana Celular/fisiologia , Membrana Celular/ultraestrutura , Embrião de Galinha , Clatrina/ultraestrutura , Invaginações Revestidas da Membrana Celular/ultraestrutura , Fibroblastos/fisiologia , Fibroblastos/ultraestrutura , Humanos , Microscopia Eletrônica , Receptores da Transferrina/genética , Transfecção , Gravação em VídeoRESUMO
OBJECTIVE: To study the effects of antenatal perineal massage on subsequent perineal outcomes at delivery. DESIGN: A randomised, single-blind prospective study. SETTING: Department of Obstetrics and Gynaecology, Watford General Hospital. PARTICIPANTS: Eight hundred and sixty-one nulliparous women with singleton pregnancy and fulfilling criteria for entry to the trial between June 1994 and October 1995. RESULTS: Comparison of the group assigned to massage with the group assigned to no massage showed a reduction of 6.1% in second or third degree tears or episiotomies. This corresponded to tear rates of 75.1% in the no-massage group and 69.0% in the massage group (P = 0.073). There was a corresponding reduction in instrumental deliveries from 40.9% to 34.6% (P = 0.094). After adjustment for mother's age and infant's birthweight these reductions achieved statistical significance (P = 0.024 and P = 0.034, respectively). Analysis by mother's age showed a much larger benefit due to massage in those aged 30 and over and a smaller benefit in those under 30. CONCLUSION: Antenatal perineal massage appears to have some benefit in reducing second or third degree tears or episiotomies and instrumental deliveries. This effect was stronger in the age group 30 years and above.