Local variation in mountain birch spring phenology along an altitudinal gradient in northern coastal Fennoscandia

Currently there is a lack of spring phenology studies covering small-scale altitudinal gradients of mountain birch in coastal northern Fennoscandia, a region characterized by exceptionally high precipitation of snow, which gives reason to investigate the influence of snow cover on birch budburst in this area. Furthermore, ground phenology studies are today increasingly replaced by satellite data studies, but only too rarely is the latter approach properly validated. In order to provide a better basis for studies of local variation in spring phenology of birch in coastal altitudinal gradients, this study aimed at exploring how well (1) thermal sum models could predict budburst in individual birch trees with the inclusion of local conditions such as snow depth, soil temperature and altitude as predictors, and (2) NDVI values from high-resolution satellite images reflect leaf phenology in birch. The result for (1) showed that a simple thermal time model with spring air temperatures provided the best explanation for budburst, and that snow depth, soil temperature and altitude did not improve the predictions. The results for (2) showed that the correspondence between NDVI values and leaf phenology was generally high, but there were still some variation between in situ measurements and the satellite-derived NDVI, probably reflecting the limited capacity of satellite imagery to capture the phenology of merely one species

Size and conformation of Aβ_1–42 aggregates.

<p>(A–F) Size distributions of Aβ_1–42 aggregates at different time points, as determined with DLS. (A–D) Aβ_1–42 samples prepared with HFIP: (A, B: <i>protocol </i><i>I</i>; C, D: <i>protocol </i><i>II</i>) (E, F) Aβ_1–42 samples prepared with NaOH and incubated at pH = 7. A, C, F show samples incubated for 48 h and B, D, F show samples incubated for 4 d at room temperature. Data taken at <i>T</i> = 25±0.1°C. (G) Dot blots probed with A11 and OC antibodies show that both A11-positive and OC-positive material is contained in the Aβ_1–42 samples after 4 days of incubation. Representative blots are shown (<i>n</i>≥2 for each condition).</p

Effect of HFIP-free Aβ_1–42 oligomers (<i>NaOH protocol</i>) on Kv 1.3 current and on BLM conductance.

<p>(A) Representative K⁺ currents evoked by depolarizing voltage steps from the holding potential of −80 mV before (black) and after (red) Aβ_1–42 application. Note, that Aβ_1–42 samples aggregated for less than 1 hr and presumably contained monomeric peptide, had no effect on K⁺ current (A, <i>left</i>), whereas samples aggregated for 48 hrs produced characteristic effect on K⁺ current kinetics (A, <i>right</i>). (B–E) Activation and inactivation kinetics of K⁺ currents before (black) and after application of Aβ_1–42 oligomers (red) shown in absolute (B, D) and normalized (C, E) values of time constants at different voltages (mean ± S.E.M., <i>n</i> = 4 cells). The effect of Aβ on the activation time constant was significant in Tests of Within-Subjects Effects (F = 34.5; ^#P = 0.009, Two-way RM-ANOVA) with significant interaction between FactorA (treatment) and FactorB (voltage) (F = 38.03), and by Pairwise Comparisons at −20 mV (*P = 0.006, Tukey test). The effect of Aβ on the inactivation time constant was also significant in Tests of Within-Subjects Effects (F = 19.1; ^#P = 0.022, Two-way RM-ANOVA) with significant interaction between FactorA (treatment) and FactorB (voltage) (F = 7.1), and by Pairwise Comparisons at −20 mV (*P = 0.016, Tukey test). (F) Representative <i>I</i>/<i>V</i> curves recorded on DOPC/DOPE BLMs before (black) and after (red) application of Aβ_1–42 oligomers. (G) Dose-dependence of Aβ-induced currents at +150 mV across BLMs (mean ± S.E.M., <i>n</i> = 5 experiments, out of a total of 12, in which the effect was observed).</p

Effect of Aβ_1–42 oligomers (<i>HFIP protocol</i><i>I</i>) on Kv 1.3 currents and on BLM conductance.

<p>(A) Representative K⁺ currents evoked by depolarizing voltage steps from holding potential of −80 mV before (black) and after (red) application of Aβ_1–42 oligomers. (B) Peak K⁺ currents normalized to mean control values at different voltages before (black) and after application of Aβ_1–42 oligomers (red). Data are shown as mean ± S.E.M. (<i>n</i> = 6 cells). HFIP had no significant (n/s) effect on the peak current (F = 0.17; P = 0.69, Two-way RM-ANOVA). (C–F) Activation and inactivation kinetics of K⁺ currents before (black) and after application of Aβ_1–42 oligomers (red) shown in absolute (C, E) and normalized (D, F) values of time constants at different voltages (mean ± S.E.M., <i>n</i> = 6 cells). The effect of Aβ on the activation time constant was significant in Tests of Within-Subjects Effects (F = 46.8; ^#P = 4.7×10⁻⁴, Two-way RM-ANOVA), with significant interaction between FactorA (treatment) and FactorB (voltage) (F = 25.9), and by Pairwise Comparisons at −20 mV (*P = 2.08×10⁻⁴, Tukey test). The effect of Aβ on the inactivation time constant was also significant in Tests of Within-Subjects Effects (F = 8.1; ^#P = 0.04, Two-way RM-ANOVA), and by Pairwise Comparisons at −20 mV, −10 and 0 mV (*P<0.05; Tukey test). (G) Representative <i>I</i>/<i>V</i> curves recorded on DOPC/DOPE BLMs before (black) and after (red) application of Aβ_1–42 oligomers. (H) Dose-dependence of Aβ_1–42-induced currents at +150 mV across BLMs (mean ± S.E.M., <i>n</i> = 11 experiments, out of a total of 16, in which the effect was observed). HFIP concentrations estimated from ¹⁹F NMR spectra of the Aβ_1–42 stock solutions are shown on the top axis.</p

Effects of Aβ_1–42 oligomers (<i>HFIP protocol</i><i>II</i>) on Kv 1.3 currents and on BLM conductance.

<p>(A) Representative K⁺ currents evoked by depolarizing voltage steps from the holding potential of −80 mV before (black) and after (red) application of Aβ_1–42 oligomers. (B) Peak K⁺ currents normalized to mean control values at different voltages after application of Aβ_1–42 oligomers. The differences in peak current amplitude before and after application of Aβ are not significant (F = 3.9; P = 0.08 two-way RM-ANOVA). (C–F) Activation and inactivation kinetics of K⁺ currents before (black) and after application of Aβ_1–42 oligomers (red) shown in absolute (C, E) and normalized (D, F) values of time constants at different voltages (mean ± S.E.M., <i>n</i> = 4 cells). The effect of Aβ on the activation time constant was not significant in Tests of Within-Subjects Effects (F = 4.4; ^#P = 0.07, Two-way RM-ANOVA). ANOVA analysis also revealed no significant effect of Aβ on the inactivation time constant (F = 8.7; ^#P = 0.05, Two-way RM-ANOVA), however two-way paired t-Test, (⁺⁺P<0.05) showed significant differences between mean time constant measured before and after treatment with Aβ, revealing the trend. (G) Representative <i>I</i>/<i>V</i> curves recorded on DOPC/DOPE BLMs before (black) and after (red) application of Aβ_1–42 oligomers. (H) Dose-dependence of Aβ-induced currents at +150 mV across BLMs (mean ± S.E.M., <i>n</i> = 7 experiments, out of a total of 9, in which the effect was observed).</p

Quantification of HFIP and TFA in aqueous solutions by ¹⁹F NMR.

<p>(A) Aβ-free aqueous solution spiked with 0.1 mM HFIP. (B) Aβ-free aqueous solution spiked with 0.13 mM TFA. (C) ¹⁹F NMR spectra of Aβ_1–42 oligomer samples prepared using <i>HFIP protocol </i><i>I</i>, <i>HFIP protocol </i><i>II</i>, and the <i>NaOH protocol</i>. The signal amplification differs greatly between spectra as indicated by the different noise levels. The concentrations of Aβ_1–42 and HFIP <i>prior to evaporation</i> were 70 μM and 1.2 M. Black and red arrows indicate peaks originating from residual TFA and HFIP, respectively. (D, F) Calibration standards generated by integrating the area under the ¹⁹F peaks obtained from samples with known HFIP (D) or TFA (F) concentrations. The lines correspond to the best fits through the origin (<i>R</i>² = 0.999 for both fits). (E) HFIP concentrations ± S.E.M. in stock Aβ_1–42 samples prepared according to <i>HFIP protocols </i><i>I</i> (<i>n</i> = 6) and <i>II</i> (<i>n</i> = 7). (G) TFA concentration ± S.E.M. in stock Aβ_1–42 samples prepared according to <i>NaOH protocol</i> (<i>n</i> = 2).</p

Fibril specific, conformation dependent antibodies recognize a generic epitope common to amyloid fibrils and fibrillar oligomers that is absent in prefibrillar oligomers-0

<p><b>Copyright information:</b></p><p>Taken from "Fibril specific, conformation dependent antibodies recognize a generic epitope common to amyloid fibrils and fibrillar oligomers that is absent in prefibrillar oligomers"</p><p>http://www.molecularneurodegeneration.com/content/2/1/18</p><p>Molecular Neurodegeneration 2007;2():18-18.</p><p>Published online 26 Sep 2007</p><p>PMCID:PMC2100048.</p><p></p> reacted with OC serum which indicates that all types of fibrils and not Aβ monomer or prefibrillar oligomers react with OC. B. Dot blot analysis of Aβ42 and polyQ36 prefibrillar oligomers and fibrils. Aβ42 and polyQ fibrils only stain with OC serum, while Aβ42 and polyQ prefibrillar oligomers only react with A11

Fibril specific, conformation dependent antibodies recognize a generic epitope common to amyloid fibrils and fibrillar oligomers that is absent in prefibrillar oligomers-9

<p><b>Copyright information:</b></p><p>Taken from "Fibril specific, conformation dependent antibodies recognize a generic epitope common to amyloid fibrils and fibrillar oligomers that is absent in prefibrillar oligomers"</p><p>http://www.molecularneurodegeneration.com/content/2/1/18</p><p>Molecular Neurodegeneration 2007;2():18-18.</p><p>Published online 26 Sep 2007</p><p>PMCID:PMC2100048.</p><p></p>dicated at the top of the panel. Both fibrillar and prefibrillar oligomer samples contain bands that react with 4G8 ranging from monomer up to the size of material that accumulates at the top of the gel. OC only stains the bands from fibrillar samples of approximately dimer and above. A11 only stains the prefibrillar oligomer samples. 6E10 does not stain prefibrillar Aβ oligomer samples formed at pH 7.4 as previously reported [22]

Fibril specific, conformation dependent antibodies recognize a generic epitope common to amyloid fibrils and fibrillar oligomers that is absent in prefibrillar oligomers-7

<p><b>Copyright information:</b></p><p>Taken from "Fibril specific, conformation dependent antibodies recognize a generic epitope common to amyloid fibrils and fibrillar oligomers that is absent in prefibrillar oligomers"</p><p>http://www.molecularneurodegeneration.com/content/2/1/18</p><p>Molecular Neurodegeneration 2007;2():18-18.</p><p>Published online 26 Sep 2007</p><p>PMCID:PMC2100048.</p><p></p