Perforationen in der Cuticula von Weinbeeren als morphologischer Faktor der Botrytisresistenz

Außer bei offensichtlichen mechanischen Schäden war es nicht möglich, die Perforationen lichtmikroskopisch nachzuweisen. Nach Entfernung der Wachsschicht konnten sie jedoch im Rasterelektronenmikroskop sichtbar gemacht werden. Sie erscheinen alS rundliche Löcher mit einem Durchmesser von etwa 0,5 -2 μm.Insgesamt wurden 25 Rebsorten untersucht, u. a. diploide und tetraploide Formen derselben Zuchtstämme. Die Anzahl der Poren nimmt zwar mit der Reife der Beeren zu; sie ist bei gleicher Reife jedoch sortenspezifisch, wobei botrytisanfällige Trauben mehr Perforationen aufweisen als resistente. Tetraploide sind stets anfälliger und haben weit mehr Poren als die entsprechenden Diploiden.Das Fehlen von Poren oder deren geringe Anzahl in der Beerencuticula kann deshalb als eine mögliche Ursache der Pilzresistenz von Trauben angesehen werden.Rastermikroskopische Aufnahmen erbrachten keine Anhaltspunkte für einen enzymatischen Angriff von B. cinerea auf die Beerencuticula. In einem Fall war die Bruchstelle einer Cuticula in einem Präparat durch unbekannte Mikroorganismen angedaut und in ein schwammiges Netzwerk verwandelt worden. Durch Angriff von Botrytis konnte ein solcher Effekt jedoch nie erzielt werden. Selbst bei total verfaulten Beeren zeigte die Cuticula stets ein völlig intaktes Erscheinungsbild.Perforations in the cuticle of grape berries as a morphological factor of resistance to BotrytisPerforations in the cuticle of intact grape berries could ·be demonstrated indirectly by staining with an aqueous solution of fluoresceine, followed by a thorough rinsing in water and observation in UV light. Perforations, where the stain was able to penetrate and therefore could not be removed by rinsing, showed up as small spots of fluorescence of the berry skin.lt was generally not possible to detect perforations by light microscopy. After removing of the wax layer they could, however, be demonstrated by scanning electron microscopy (SEM). They appeared as roundish holes with smooth margins and a diameter of 0.5-2 μm.A total of 25 grape varieties were investigated, including diploid and tetraploid forms of the same variety. The number of holes was increasing during maturation of the grapes, their relative number was, however, specific for the variety, those with a high susceptibility to Botrytis exhibiting more perforations than resistant ones. All diploids were more resistant and also had much less perforations than the corresponding tetraploids.A Jack or a small number of perforations in the cuticle is therefore considered to be a prerequisite for fungus resistance of grape berries in most cases.SEM images did not indicate enzymatical attack of the cuticle by Botrytis. In one case, where the edge of the cuticle was digested by unknown microorganisms, a spongy skeleton was left back, whereas the cuticular structure of berries infected with Botrytis never showed any differences to those of healthy ones

Eine neue Methode zur Mostgewichtsbestimmung und Klassifizierung unverletzter Weinbeeren

Das Mostgewicht von Weinbeeren kann mit Hilfe von Lösungen definierter Dichte ohne Verletzung der Beerenhaut bestimmt werden. Dadurch wird eine schnelle und einfache Klassifizierung großer Beerenmengen nach deren Reifegrad ermöglicht. Die Leistungsfähigkeit der Methode wurde durch Bestimmung der Reifeverteilung bei Beeren von 10 Rebsorten zu definierten Zeitpunkten belegt; die Werte wurden durch Vergleich mit refraktometrisch ermittelten Daten überprüft. Das Verfahren schafft die Voraussetzung für vergleichende Routineuntersuchungen der BotrytisResistenz von Rebsorten.A novel method for non-destructive determination of the sogar content and for classification of grape berriesThe sugar degree of grape berries was determined by fractionation with defined solutions of different density without injury of the berry. This method allows the classification of !arge amounts of berries according to their maturity.The efficiency of the method was proved by the determination of different classes of maturity in berries of 10 grape varieties at a given time. The values were compared with data obtained by refractometrical determinations. Density fractionation is the prerequisite for the comparison of the resistance against Botrytis cinerea of grape varieties on a !arge scale

Ab-initio theory of NMR chemical shifts in solids and liquids

We present a theory for the ab-initio computation of NMR chemical shifts (sigma) in condensed matter systems, using periodic boundary conditions. Our approach can be applied to periodic systems such as crystals, surfaces, or polymers and, with a super-cell technique, to non-periodic systems such as amorphous materials, liquids, or solids with defects. We have computed the hydrogen sigma for a set of free molecules, for an ionic crystal, LiH, and for a H-bonded crystal, HF, using density functional theory in the local density approximation. The results are in excellent agreement with experimental data.Comment: to appear in Physical Review Letter

Atomistic Studies of Defect Nucleation during Nanoindentation of Au (001)

Atomistic studies are carried out to investigate the formation and evolution of defects during nanoindentation of a gold crystal. The results in this theoretical study complement the experimental investigations [J. D. Kiely and J. E. Houston, Phys. Rev. B, v57, 12588 (1998)] extremely well. The defects are produced by a three step mechanism involving nucleation, glide and reaction of Shockley partials on the {111} slip planes noncoplanar with the indented surface. We have observed that slip is in the directions along which the resolved shear stress has reached the critical value of approximately 2 GPa. The first yield occurs when the shear stresses reach this critical value on all the {111} planes involved in the formation of the defect. The phenomenon of strain hardening is observed due to the sessile stair-rods produced by the zipping of the partials. The dislocation locks produced during the second yield give rise to permanent deformation after retraction.Comment: 11 pages, 13 figures, submitted to Physical Review

Dephasing of Electrons by Two-Level Defects in Quantum Dots

The electron dephasing time $\tau_{\phi}$ in a diffusive quantum dot is calculated by considering the interaction between the electron and dynamical defects, modelled as two-level system. Using the standard tunneling model of glasses, we obtain a linear temperature dependence of $1/\tau_{\phi}$, consistent with the experimental observation. However, we find that, in order to obtain dephasing times on the order of nanoseconds, the number of two-level defects needs to be substantially larger than the typical concentration in glasses. We also find a finite system-size dependence of $\tau_{\phi}$, which can be used to probe the effectiveness of surface-aggregated defects.Comment: two-column 9 page

Stress avulsion of the tibial tuberosity after tension band wiring of a patellar fracture: a case report

INTRODUCTION: To the best of our knowledge there is no other report of an elderly patient who was surgically treated for a patellar fracture with tension band wiring and who subsequently suffered from an avulsion fracture of the tibial tuberosity. The combination of a patellar fracture and avulsion of the patellar ligament has only been described as complication after bone-patellar tendon-bone anterior cruciate ligament reconstructions. However, due to demographic changes and more elderly patients treated this injury may become more frequent in future. CASE PRESENTATION: We present the case of an 81 year old female who sustained an oblique patellar fracture after a direct contact injury of the left knee when falling on ice. Consequently the patellar fracture was openly reduced and stabilized with tension band wiring. The follow-up was uneventful till three months after surgery when the patient noticed a spontaneous avulsion fracture of the tibial tuberosity (Ogden type 3). The tibial tuberosity fragment was reattached with two non-resorbable sutures looped around two modified AO cortical 3.5 mm long neck screws. Intraoperatively multiple bone cysts were seen. Biopsies were not taken to prevent further fragmentation of the tibial tuberosity. The patient was followed up with anteroposterior and lateral full weight bearing radiographs and clinical assessment at 6, 12 weeks and 6 months after surgery. Recovery was completely pain free with full satisfaction. CONCLUSION: In conclusion in elderly patients with a patella fracture a possible associated but not obvious fracture of the tibial tuberosity should be ruled out and the postoperative rehabilitation protocol after tension band wiring of the patella might have to be individually adjusted to bone quality and course of the fracture

Assessment of synaptic loss in mouse models of β-amyloid and tau pathology using [18F]UCB-H PET imaging

Objective: In preclinical research, the use of [F-18]Fluorodesoxyglucose (FDG) as a biomarker for neuro-degeneration may induce bias due to enhanced glucose uptake by immune cells. In this study, we sought to investigate synaptic vesicle glycoprotein 2A (SV2A) PET with [F-18]UCB-H as an alternative preclinical biomarker for neurodegenerative processes in two mouse models representing the pathological hallmarks of Alzheimer's disease (AD). Methods: A total of 29 PS2APP, 20 P301S and 12 wild-type mice aged 4.4 to 19.8 months received a dynamic [F-18]UCB-H SV2A-PET scan (14.7 +/- 1.5 MBq) 0-60 min post injection. Quantification of tracer uptake in cortical, cerebellar and brainstem target regions was implemented by calculating relative volumes of distribution (V-T) from an image-derived-input-function (IDIF). [F-18]UCB-H binding was compared across all target regions between transgenic and wild-type mice. Additional static scans were performed in a subset of mice to compare [F-18]FDG and [F-18]GE180 (18 kDa translocator protein tracer as a surrogate for microglial activation) standardized uptake values (SUV) with [F-18]UCB-H binding at different ages. Following the final scan, a subset of mouse brains was immunohistochemically stained with synaptic markers for gold standard validation of the PET results. Results: [F-18]UCB-H binding in all target regions was significantly reduced in 8-months old P301S transgenic mice when compared to wild-type controls (temporal lobe: p = 0.014;cerebellum: p = 0.0018;brainstem: p = 0.0014). Significantly lower SV2A tracer uptake was also observed in 13-months (temporal lobe: p = 0.0080;cerebellum: p = 0.006) and 19-months old (temporal lobe: p = 0.0042;cerebellum: p = 0.011) PS2APP transgenic versus wild-type mice, whereas the brainstem revealed no significantly altered [F-18]UCB-H binding. Immunohistochemical analyses of post-mortem mouse brain tissue confirmed the SV2A PET findings. Correlational analyses of [F-18]UCB-H and [F-18]FDG using Pearson's correlation coefficient revealed a significant negative association in the PS2APP mouse model (R = -0.26, p = 0.018). Exploratory analyses further stressed microglial activation as a potential reason for this inverse relationship, since [F-18]FDG and [F-18]GE180 quantification were positively correlated in this cohort (R = 0.36, p = 0.0076). Conclusion: [F-18]UCB-H reliably depicts progressive synaptic loss in PS2APP and P301S transgenic mice, potentially qualifying as a more reliable alternative to [F-18]FDG as a biomarker for assessment of neuro-degeneration in preclinical research

Interaction effects and phase relaxation in disordered systems

This paper is intended to demonstrate that there is no need to revise the existing theory of the transport properties of disordered conductors in the so-called weak localization regime. In particular, we demonstrate explicitly that recent attempts to justify theoretically that the dephasing rate (extracted from the magnetoresistance) remains finite at zero temperature are based on the profoundly incorrect calculation. This demonstration is based on a straightforward evaluation of the effect of the electron-electron interaction on the weak localization correction to the conductivity of disordered metals. Using well-controlled perturbation theory with the inverse conductance $g$ as the small parameter, we show that this effect consists of two contributions. First contribution comes from the processes with energy transfer smaller than the temperature. This contribution is responsible for setting the energy scale for the magnetoresistance. The second contribution originates from the virtual processes with energy transfer larger than the temperature. It is shown that the latter processes have nothing to do with the dephasing, but rather manifest the second order (in $1/g$) correction to the conductance. This correction is calculated for the first time. The paper also contains a brief review of the existing experiments on the dephasing of electrons in disordered conductors and an extended qualitative discussion of the quantum corrections to the conductivity and to the density of electronic states in the weak localization regime.Comment: 34 pages, 13 .eps figure

Selective Induction of DNA Repair Pathways in Human B Cells Activated by CD4+ T Cells

Greater than 75% of all hematologic malignancies derive from germinal center (GC) or post-GC B cells, suggesting that the GC reaction predisposes B cells to tumorigenesis. Because GC B cells acquire expression of the highly mutagenic enzyme activation-induced cytidine deaminase (AID), GC B cells may require additional DNA repair capacity. The goal of this study was to investigate whether normal human B cells acquire enhanced expression of DNA repair factors upon AID induction. We first demonstrated that several DNA mismatch repair, homologous recombination, base excision repair, and ATR signaling genes were overexpressed in GC B cells relative to naïve and memory B cells, reflecting activation of a process we have termed somatic hyperrepair (SHR). Using an in vitro system, we next characterized activation signals required to induce AID expression and SHR. Although AID expression was induced by a variety of polyclonal activators, SHR induction strictly required signals provided by contact with activated CD4+ T cells, and B cells activated in this manner displayed reduced levels of DNA damage-induced apoptosis. We further show the induction of SHR is independent of AID expression, as GC B cells from AID -/- mice retained heightened expression of SHR proteins. In consideration of the critical role that CD4+ T cells play in inducing the SHR process, our data suggest a novel role for CD4+ T cells in the tumor suppression of GC/post-GC B cells