2,240 research outputs found
Resolution in the ApoTome and the confocal laser scanning microscope: comparison
No full textThe essential feature of the confocal laser scanning microscope (cLSM) is the generation of optical sections by the removal of out-of-focus light. About ten years ago, structured illumination microscopy (SIM) was introduced as an alternative method for obtaining optical sections from biological specimens. Here we compare the resolution of the ApoTome (commercial SIM by Zeiss) to that achieved by a cLSM (Zeiss LSM 510). If fluorescent beads are used as test objects, then the ApoTome will achieve a lower axial resolution than the cLSM. In contrast to that, its lateral resolution scores slightly better. If subresolution homogeneous fluorescent layers are used as test objects, then the ApoTome will achieve a higher axial resolution than the cLSM. The ApoTome's axial resolution is homogeneous over the field-of-view while that of the cLSM changes markedly. Finally, the anisotropy of the ApoTome's resolution was found to be negligible for standard applications while its capability to resolve fine structures within stained tissue slices is limited to one or two cell layers and thus worse than in the cLSM. (C) 2009 Society of Photo-Optical Instrumentation Engineers. [DOI: 10.1117/1.3083439]Deutsche Forschungsgemeinschaf
Errata: Resolution in the ApoTome and the confocal laser scanning microscope: comparison
No full textLocal Church Week Pastor Andre Mitchell
No full textPastor Andre Mitchell, Pastor, Author, CEO, Deliverance Temple/Andre Mitchell Ministries, Muncie, IN, speaks on how connecting with other believers is important to your faith for Local Church Week
An Ion-insensitive cAMP Biosensor for Long Term Quantitative Ratiometric Fluorescence Resonance Energy Transfer (FRET) Measurements under Variable Physiological Conditions
No full textRatiometric measurements with FRET-based biosensors in living cells using a single fluorescence excitation wavelength are often affected by a significant ion sensitivity and the aggregation behavior of the FRET pair. This is an important problem for quantitative approaches. Here we report on the influence of physiological ion concentration changes on quantitative ratiometric measurements by comparing different FRET pairs for a cAMP-detecting biosensor. We exchanged the enhanced CFP/enhanced YFP FRET pair of an established Epac1-based biosensor by the fluorophores mCerulean/mCitrine. In the case of enhanced CFP/enhanced YFP, we showed that changes in proton, and (to a lesser extent) chloride ion concentrations result in incorrect ratiometric FRET signals, which may exceed the dynamic range of the biosensor. Calcium ions have no direct, but an indirect pH-driven effect by mobilizing protons. These ion dependences were greatly eliminated when mCerulean/mCitrine fluorophores were used. For such advanced FRET pairs the biosensor is less sensitive to changes in ion concentration and allows consistent cAMP concentration measurements under different physiological conditions, as occur in metabolically active cells. In addition, we verified that the described FRET pair exchange increased the dynamic range of the FRET efficiency response. The time window for stable experimental conditions was also prolonged by a faster biosensor expression rate in transfected cells and a greatly reduced tendency to aggregate, which reduces cytotoxicity. These properties were verified in functional tests in single cells co-expressing the biosensor and the 5-HT1A receptor
Ratiometric high-resolution imaging of JC-1 fluorescence reveals the subcellular heterogeneity of astrocytic mitochondria
No full textUsing the mitochondrial potential (ΔΨ(m)) marker JC-1 (5,5',6,6'-tetrachloro-1,1',3,3'-tetraethylbenzimidazolylcarbocyanine iodide) and high-resolution imaging, we functionally analyzed mitochondria in cultured rat hippocampal astrocytes. Ratiometric detection of JC-1 fluorescence identified mitochondria with high and low ΔΨ(m). Mitochondrial density was highest in the perinuclear region, whereas ΔΨ(m) tended to be higher in peripheral mitochondria. Spontaneous ΔΨ(m) fluctuations, representing episodes of increased energization, appeared in individual mitochondria or synchronized in mitochondrial clusters. They continued upon withdrawal of extracellular Ca(2+), but were antagonized by dantrolene or 2-aminoethoxydiphenylborate (2-APB). Fluo-3 imaging revealed local cytosolic Ca(2+) transients with similar kinetics that also were depressed by dantrolene and 2-APB. Massive cellular Ca(2+) load or metabolic impairment abolished ΔΨ(m) fluctuations, occasionally evoking heterogeneous mitochondrial depolarizations. The detected diversity and ΔΨ(m) heterogeneity of mitochondria confirms that even in less structurally polarized cells, such as astrocytes, specialized mitochondrial subpopulations coexist. We conclude that ΔΨ(m) fluctuations are an indication of mitochondrial viability and are triggered by local Ca(2+) release from the endoplasmic reticulum. This spatially confined organelle crosstalk contributes to the functional heterogeneity of mitochondria and may serve to adapt the metabolism of glial cells to the activity and metabolic demand of complex neuronal networks. The established ratiometric JC-1 imaging-especially combined with two-photon microscopy-enables quantitative functional analyses of individual mitochondria as well as the comparison of mitochondrial heterogeneity in different preparations and/or treatment conditions
Analysis of FRET-signals in the presence of free donors and acceptors.
No full textAbstractA method for spectral analysis of Förster resonance energy transfer (FRET) signals is presented, taking into consideration both the contributions of unpaired donor and acceptor fluorophores and the influence of incomplete labeling of the interacting partners. It is shown that spectral analysis of intermolecular FRET cannot yield accurate values of the Förster energy transfer efficiency E, unless one of the interactors is in large excess and perfectly labeled. Instead, analysis of donor quenching yields a product of the form Efdpa, where fd is the fraction of donor-type molecules participating in donor-acceptor complexes and pa is the labeling probability of the acceptor. Similarly, analysis of sensitized emission yields a product involving Efa. The analysis of intramolecular FRET (e.g., of tandem constructs) yields the product Epa. We use our method to determine these values for a tandem construct of cyan fluorescent protein and yellow fluorescent protein and compare them with those obtained by standard acceptor photobleaching and fluorescence lifetime measurements. We call the method lux-FRET, since it relies on linear unmixing of spectral components
Pearl Andre, Political Activist and Author from Bismarck
No full textAn undated photograph of Pearl Andre, an author and political activist from Bismarck. She wrote the book Women on the Move about the Nonpartisan League in North Dakota in 1975.https://commons.und.edu/nd-politics-photos/1254/thumbnail.jp
Andre Gide and the Negro, 1940
No full textBecause it is generally known that Andre Gide is one of France's most influential contemporary writers, there is no need to justify a study based on his works. Desirous of obtaining the opinion of an influential white author concerning Negroid people and learning his activities in their behalf, the writer of this thesis undertook the study, Andre Gide end the Negro. The value of such a study to the American Negro lies primarily in (1) a better acquaintance with and appreciation for one whose interest in darker people has resulted in a tangible contribution; (2) a knowledge of the condition of a people, who, though distant in territory, are kindred in race, and (3) a challenge for scholastic accomplishment. The method of procedure was a careful analysis of Voyage au Congo and Retour du Tchad supplemented by collateral readings. To secure information concerning Mr. Gide's official investigation in 1938 of the natives' educational facilities in Senegal, a letter was sent him. Despite the anxiety which must be his because of the present war in which his country is involved, the eminent author found time to respond. His reply is quoted on page thirty-one of this study. Grateful acknowledgment is hereby given both Mr. Gide for his amicable letter and Professor Cook, who made such a contact possible. The various factors for the evolution of Gide's interest in Negroid people are shown in Chapter I. Chapter II contains a discussion of the colonial abuses existing in French Equatorial Africa exposed by Gide and his efforts to eradicate these. Through Chapter III one learns the author's personal impression of the morale and intelligence of Negroid people. In Chapter IV an interpretation of Gide's literary art in Voyage au Gang and Retour du Tchad is presented. The results are summarized in the conclusion
Quantitative Measurement of cAMP Concentration Using an Exchange Protein Directly Activated by a cAMP-Based FRET-Sensor
No full textAbstractFörster resonance energy transfer (FRET)-based biosensors for the quantitative analysis of intracellular signaling, including sensors for monitoring cyclic adenosine monophosphate (cAMP), are of increasing interest. The measurement of the donor/acceptor emission ratio in tandem biosensors excited at the donor excitation wavelength is a commonly used technique. A general problem, however, is that this ratio varies not only with the changes in cAMP concentration but also with the changes of the ionic environment or other factors affecting the folding probability of the fluorophores. Here, we use a spectral FRET analysis on the basis of two excitation wavelengths to obtain a reliable measure of the absolute cAMP concentrations with high temporal and spatial resolution by using an “exchange protein directly activated by cAMP”. In this approach, FRET analysis is simplified and does not require additional calibration routines. The change in FRET efficiency (E) of the biosensor caused by [cAMP] changes was determined as ΔE=15%, whereas E varies between 35% at low and 20% at high [cAMP], allowing quantitative measurement of cAMP concentration in the range from 150 nM to 15μM. The method described is also suitable for other FRET-based biosensors with a 1:1 donor/acceptor stoichiometry. As a proof of principle, we measured the specially resolved cAMP concentration within living cells and determined the dynamic changes of cAMP levels after stimulation of the Gs-coupled serotonin receptor subtype 7 (5-HT7)
Forholdet mellom fugler og vindmøller og andre lufthindringer. En litteraturoversikt
No full textNygård, T, Bevanger, K. & Reitan, O. 2008. Forholdet mellom fug-ler og vindmøller og andre lufthindringer. En litteraturoversikt. - NINA Rapport 413. 167 s.
Rapporten er en trykt versjon av en nettbasert referansedatabase om forholdet mellom fugl og flaggermus og vindmøller, kraftledninger, tårn, bygninger og andre lufthindringer. Den er en database som blir jevnilig oppdatert, og som er tilgjengelig over nettet via EndNote Web. Referansedatabasen inneholder i skrivende stund 1224 referanser til litteratur som omhandler denne problematikken. Databasen blir stadig utvidet etter hvert som ny litteratur blir tilgjengelig. Basen kan brukes som søkeverktøy mot andre litteraturdatabaser så som ISI Web of knowledge, Biosis og lignende, avhengig av brukertilgang. . I denne trykte utgaven er referansene sortert tematisk, deretter på trykkeår og forfatter. Basen har fått navnet ”Birdwind”. og oppdateres og administreres av NINA. Basen er ment som er verktøy som gjør det lettere å finne fram til relevant litteratur innenfor disse raskt voksende temaene. database, referanser, internett, EndNote web, fugl, flaggermus, vindmøller, vindkraft, kraftledninger, tårn, bygninger, gjerder, lufthindringer, radar, fugletrekk, kollisjoner, risiko, unnvikelse, økologiske effekter, avbøtende tiltak, litteratur, database, references, internet, EndNote Web, birds, bats, wind-farms, wind energy, turbines, utility structures, towers, buildings, fences, aerial obstacles, collisions, risk, radar, bird migration, avoidance, ecological effects, mitigation measures, literatureNygård, T., Bevanger, K. & Reitan, O. 2008. The relation between birds and wind turbines and other aerial obstacles. A literature survey. - NINA Report 413. 167 pp.
The report is a printed version of an internet-based reference database on the relation between birds and bats and aerial obstacles such as wind turbines, utility structures, towers and buildings. The database will be updated regularly, and is accessible via EndNote Web. At the date of printing it contains 1224 references on these topics. The database can also be used as a search engine for other databases such as ISI Web of knowledge, Biosis and others, depending on the access rights of the user.
In this printed version, the references are sorted by theme, thereafter by year of printing and author. The database is named “Birdwind”, and is administered and updated by NINA. The database is meant to be a tool that will make it easier to find relevant literature within these rapidly growing topics
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