6,593 research outputs found
Yeast metabolism in fresh and frozen dough : a thesis presented in partial fulfilment of the requirements for the degree of Doctor of Philosophy in Food Technology at Massey University, Palmerston North, New Zealand
Get PDFAuthor also known as SM LovedayFresh bakery products have a very short shelf life, which limits the extent to which manufacturing can be centralised. Frozen doughs are relatively stable and can be manufactured in large volumes, distributed and baked on-demand at the point of sale or consumption. With appropriate formulation and processing a shelf life of several months can be achieved.Shelf life is limited by a decline in proofing rate after thawing, which is attributed to a) the dough losing its ability to retain gas and b) insufficient gas production, i.e. yeast activity. The loss of shelf life is accelerated by delays between mixing and freezing, which allow yeast cells the chance to ferment carbohydrates.This work examined the reasons for insufficient gas production after thawing frozen dough and the effect of pre-freezing fermentation on shelf life. Literature data on yeast metabolite dynamics in fermenting dough were incomplete. In particular there were few data on the accumulation of ethanol, a major fermentation end product which can be injurious to yeast.Doughs were prepared in a domestic breadmaker using compressed yeast from a local manufacturer and analysed for glucose, fructose, sucrose, maltose and ethanol. Gas production after thawing declined within 48 hours of frozen storage. This was accelerated by 30 or 90 minutes of fermentation at 30;C prior to freezing.Sucrose was rapidly hydrolysed and yeast consumed glucose in preference to fructose. Maltose was not consumed while other sugars remained. Ethanol, accumulated from consumption of glucose and fructose, was produced in approximately equal amounts to CO2, indicating that yeast cells metabolised reductively.Glucose uptake in fermenting dough followed simple hyperbolic kinetics and fructose uptake was competitively inhibited by glucose. Mathematical modelling indicated that diffusion of sugars and ethanol in dough occurred quickly enough to eliminate solute gradients brought about by yeast metabolism
Development of saccadic suppression in children
No full textWe measured saccadic suppression in adolescent children and young adults using spatially curtailed low spatial frequency stimuli. For both groups, sensitivity for color-modulated stimuli was unchanged during saccades. Sensitivity for luminance-modulated stimuli was greatly reduced during saccades in both groups but far more for adolescents than for young adults. Adults' suppression was on average a factor of about 3, whereas that for the adolescent group was closer to a factor of 10. The specificity of the suppression to luminance-modulated stimuli excludes generic explanations such as task difficulty and attention. We suggest that the enhanced suppression in adolescents results from the immaturity of the ocular-motor system at that age
Converting SrI <sub>2</sub> :Eu <sup>2+</sup> into a near infrared scintillator by Sm <sup>2+</sup> co-doping
No full text The luminescence and scintillation properties of SrI 2 single crystals doped with 5% Eu 2+ and 0.05%, 0.2% and 0.5% Sm 2+ are evaluated. X-ray excited and photoluminescence measurements show energy transfer from excited Eu 2+ ions to Sm 2+ ions. At a concentration of 0.5% Sm 2+ , the luminescence consists almost entirely of 740 nm emission from Sm 2+ 5d-4f transitions. Co-doping SrI 2 :5% Eu 2+ with Sm 2+ provides a novel method to bypass the self-absorption problem encountered in large SrI 2 :Eu 2+ crystals and, at the same time, provides a unique near-infrared emitting scintillator with a light yield of approximately 40,000 photons/MeV. Accepted Author ManuscriptRST/Fundamental Aspects of Materials and EnergyRST/Luminescence Material
'Laws 'Needefull in Later to be Abrogated': Intersex and the Sources of Christian Theology
No full textThis is the author accepted manuscript. The final version is available from Palgrave Macmillan via the DOI in this record
Introduction: Troubling Bodies?
No full textThis is the author accepted manuscript. The final version is available from Palgrave Macmillan via the DOI in this record
CONSORT_2010_Checklist_completed – Supplemental material for Brain circuitry, behavior, and cognition: A randomized placebo-controlled trial of donepezil in fragile X syndrome
No full textSupplemental material, CONSORT_2010_Checklist_completed for Brain circuitry, behavior, and cognition: A randomized placebo-controlled trial of donepezil in fragile X syndrome by Jennifer L Bruno, SM Hadi Hosseini, Amy A Lightbody, Mai K Manchanda and Allan L Reiss in Journal of Psychopharmacology</p
Supplement_0503 – Supplemental material for Brain circuitry, behavior, and cognition: A randomized placebo-controlled trial of donepezil in fragile X syndrome
No full textSupplemental material, Supplement_0503 for Brain circuitry, behavior, and cognition: A randomized placebo-controlled trial of donepezil in fragile X syndrome by Jennifer L Bruno, SM Hadi Hosseini, Amy A Lightbody, Mai K Manchanda and Allan L Reiss in Journal of Psychopharmacology</p
Valutazione di ceppi mutanti di S. TYPHIMURIUM e di M. GALLOPROVINCIALIS come sistemi per la caratterizzazione tossicologica di nanoparticelle di ampio utilizzo
Get PDFA variety of nanomaterials are currently in use or under development in our society. Small size, particular shape, large surface area and activity make them attractive to different application fields, ranging from medical products to industrial processes.
Owing to the unique chemico-physical properties, the most common nanoparticles lack of adequate toxicological characterization in different biological systems. To date, first-level assays for the detection of possible cytotoxic and genotoxic effects have not yet identified and validated. The European Centre for the Sustainable Impact of Nanotechnology (ECSIN) was created to ascertain the biological risks related to the use of nanoparticles (NPs) by in vitro and in vivo studies on prokaryotic and eukaryotic cells (only fragmentary or conflicting data were available for bacterial cells at the start of this study).
Aiming to evaluate the suitability of protocols based on rfa mutant Salmonella thyphimurium cells, Ludox® silica NPs were tested on the strains TA 98, TA 100 (plate and fluctuation test) and TA 1535 pSK1002 (SOS umu test). Following incubation with log-phase TA 100 cells at 37 °C in PBS, flow cytometry and fluorimetric measures were carried out to estimate the intracellular uptake of Qtracker®800 and fluorescein-loaded silica NPs. The incubation with these NPs slightly increased the fluorescence associated to bacterial cells after 3-6 h and 3-11 h of contact, respectively. Possible internalization of electron-dense quantum dots and γFe2O3 was also studied by TEM imaging. Although partially cytotoxic, the silica NPs did not induce mutagenic or genotoxic effects, nor the γFe2O3 did it. The inability of the tested particles to enter the mutant bacterial cells can explain the overall results, as confirmed by the TEM images. NP-related oxidative stress with indirect alteration of cellular functions cannot be excluded.
Hence protocols based on prokaryotes are not suitable for routine NP testing, however they could be rationally used to characterize the combined effect of NPs and genotoxic components occurring together in complex environmental mixtures. For instance, in our hands, γFe2O3 significantly attenuated the mutagenic effects directly induced by hexavalent (K2Cr2O7) on TA 100 cells.
As alternative experimental model, we considered haemocytes and other cell types of the marine invertebrate Mytilus galloprovincialis, already used as sentinel organism in environmental studies.
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Preliminary data obtained with the Single-Cell gel Electrophoresis (Comet Assay) and Micronucleus test support the use of both assays as a first-screening tools for assessing the DNA damage possibly induced by industrial NPs.4
Nonostante il rapido sviluppo e il molteplice utilizzo di una varietà di nanoparticelle e nanomateriali, a tutt‟oggi mancano regolamentazione adeguata e protocolli standard per la loro caratterizzazione tossicologica. In questi anni, il centro di ricerca ECSIN (The European Centre for the Sustainable Impact of Nanotechnology) si è fatto promotore di studi in vitro e in vivo volti ad accertare i rischi biologici associabili a NP di ampio uso industriale, definendo tra gli altri obiettivi la valutazione di specifiche NP in cellule procariotiche ed eucariotiche.
Benchè i batteri siano incapaci di endocitosi, alcuni dati conflittuali e la frammentarietà delle informazioni disponibili all‟inizio di questo studio hanno indotto a considerare come potenziale sistema bersaglio cellule derivate da S. thyphimurium LT2, mutanti rfa caratterizzati da sintesi difettiva delle catene polisaccaridiche dell‟LPS, lipopolisaccaride di membrana.
Le Ludox® sono NP di silice di ampio utilizzo e di interesse prioritario in ECSIN. Esse vengono usate nella chiarificazione delle bevande e come additivi in polimeri, vernici, rivestimenti e detergenti per la loro capacità di migliorare le proprietà di resistenza, brillantezza e adesione delle superfici e recentemente in prodotti cosmetici. Ludox® AS 30 e SM 30, caratterizzate per diametro dinamico e potenziale zeta, sono state incubate con cellule TA 98 e TA 100 per 30 minuti in soluzione salina tamponata a 37°C. Rispetto alle NP come tali, quelle sottoposte ad ultrafiltrazione sono risultate meno citotossiche. Saggiate per attività mutagena sugli stessi ceppi (plate incorporation test) le Ludox® sono risultate innocue, indipendentemente dalla presenza della frazione microsomiale S9. Per una valutazione più esauriente, le NP AS 30 e SM 30 sono state saggiate anche in micropiastra (Ames fluctuation test) e nell‟SOS/ umu test, saggi che hanno confermato l‟incapacità di indurre, rispettivamente, mutazioni o danno al DNA.
Per accertare se anche le cellule LPS-difettive escludessero le NP sono state applicate altre tecniche sperimentali. NP elettrondense quali Qtracker®800 e maghemite (γ Fe203) sono state incubate con le cellule TA 100 per 30 minuti e per 6 ore procedendo quindi a visualizzarle al TEM, analisi che hanno dimostrato l‟esclusione di entrambe le NP.
Dati ottenuti in citometria a flusso incubando NP di silice marcate con fluoresceina oppure Qtracker®800 con cellule TA 100 in PBS a 37°C per 0.5-24 ore hanno rivelato una percentuale molto modesta di cellule fluorescenti.
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A compendio del lavoro svolto, e per suggerire un uso alternativo dei test sopra illustrati, è stata valutata l‟interazione tra NP (γ Fe203) e ioni cromato (K2Cr2O7).
L‟incubazione in PBS di maghemite e bicromato di potassio in dosi combinate ha dimostrato che le nanoparticelle causano una significativa attenuazione dell‟attività mutagena del cromo esavalente.
Come approccio sperimentale alternativo, è stata messa a punto l‟analisi di danno al DNA in emociti di Mytilus galloprovincialis, un invertebrato marino già ampiamente usato come organismo sentinella dell‟ambiente costiero e che sta emergendo come modello anche per lo studio dell‟immunità innata. I primi risultati ottenuti con le particelle Ludox® indicano un aumento di frammentazione del DNA negli emociti trattati rispetto al controllo, più accentuato per le SM 30 rispetto alle AS 30. L‟individuazione di danno genetico in cellule di mitilo è stato consolidato ottimizzando l‟analisi della frequenza di cellule micronucleate come indice di danno cromosomico
Intrafullerene electron transfers in Sm-containing metallofullerenes: Sm@C-2n (74 <= 2n <= 84)
No full textThe electronic properties of Sm-containing metallofullerenes, Sm@C-74, Sm@C-76 (I, II), Sm@C-78, Sm@C-80, Sm@C-82 (I, II, III) and Sm@C-84 (I, II, III), are characterized by UV-Vis-NIR absorption spectroscopy and electron energy-loss spectroscopy (EELS). the UV-Vis-NIR absorption spectra of Sm@C-74, Sm@C-80, Sm@C-82 (I, II, III) and Sm@C-84 (I, II) are quite similar to those of the corresponding Ca, Sr, Ba, Eu, Tm, Yb-based metallofullerenes. In contrast, the absorption spectra of Sm@C-76 (I, II), Sm@C-78 and Sm@C-84(III) show a novel feature: the onset for Sm@C-78 is observed similar to 2600 nm, which corresponds to a small band gap (similar to0.5 eV). Furthermore, the oxidation states of Sm atom in the various fullerene cages are investigated by EELS, which reveals that the Sm atom takes +2 oxidation state in the fullerene cages. A probable rationale for the tendency to have the Sm2+ state is presented based on a simple thermochemical cycle model. (C) 2001 by Elsevier Science Inc.http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000168906500014&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=8e1609b174ce4e31116a60747a720701Biochemical Research MethodsBiochemistry & Molecular BiologyComputer Science, Interdisciplinary ApplicationsCrystallographyMathematical & Computational BiologySCI(E)EI30ARTICLE2244-2511
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