Preventive effect of ozone on the development of white spot lesions during multibracket appliance therapy

OBJECTIVE: To test the null hypotheses: (1) there is no difference in the caries protective effect of ozone and Cervitec/Fluor Protector during multibracket (MB) appliance therapy, and (2) DIAGNOdent and quantitative light-induced fluorescence (QLF) are not superior to a visual evaluation of initial caries lesions. MATERIALS AND METHODS: Twenty right-handed patients with a very poor oral hygiene who required full MB appliance therapy were analyzed during 26 months. In a split-mouth-design, the four quadrants of each patient were either treated with ozone, a combination of Cervitec and Fluor Protector, or served as untreated controls. The visible plaque index (VPI) and white spot formation were analyzed clinically. DIAGNOdent and QLF were used for a quantitative assessment of white spot formation. RESULTS: The average VPI in all four dental arch quadrants amounted to 55.6% and was independent of the preventive measure undertaken. In the quadrants treated with Cervitec/Fluor Protector, only 0.7% of the areas developed new, clinically visible white spots. This was significantly (P < .05) less than in the quadrants treated with ozone (3.2%). The lesions detected with QLF only partially corresponded to the clinically detected white spots, while DIAGNOdent proved to be unable to detect any changes at all. CONCLUSIONS: The caries protective effect of Cervitec/Fluor Protector during MB therapy was superior to ozone, and a visual evaluation of initial caries lesions was superior to both DIAGNOdent and QLF.

Assessing vegetation cover and biomass in restored erosion areas in Iceland using SPOT satellite data

Due to highly erodible volcanic soils and a harsh climate, livestock grazing in Iceland has led to serious soil erosion on about 40% of the country's surface. Over the last 100 years, various revegetation and restoration measures were taken on large areas distributed all over Iceland in an attempt to counteract this problem. The present research aimed to develop models for estimating percent vegetation cover (VC) and aboveground biomass (AGB) based on satellite data, as this would make it possible to assess and monitor the effectiveness of restoration measures over large areas at a fairly low cost. Models were developed based on 203 vegetation cover samples and 114 aboveground biomass samples distributed over five SPOT satellite datasets. All satellite datasets were atmospherically corrected, and digital numbers were converted into ground reflectance. Then a selection of vegetation indices (VIs) was calculated, followed by simple and multiple linear regression analysis of the relations between the field data and the calculated VIs. Best results were achieved using multiple linear regression models for both %VC and AGB. The model calibration and validation results showed that R2 and RMSE values for most VIs do not vary very much. For percent VC, R2 values range between 0.789 and 0.822, leading to RMSEs ranging between 15.89% and 16.72%. For AGB, R2 values for low-biomass areas (AGB < 800 g/m2) range between 0.607 and 0.650, leading to RMSEs ranging between 126.08 g/m2 and 136.38 g/m2. The AGB model developed for all areas, including those with high biomass coverage (AGB > 800 g/m2), achieved R2 values between 0.487 and 0.510, resulting in RMSEs ranging from 234 g/m2 to 259.20 g/m2. The models predicting percent VC generally overestimate observed low percent VC and slightly underestimate observed high percent VC. The estimation models for AGB behave in a similar way, but over- and underestimation are much more pronounced. These results show that it is possible to estimate percent VC with high accuracy based on various VIs derived from SPOT satellite data. AGB of restoration areas with low-biomass values of up to 800 g/m2 can likewise be estimated with high accuracy based on various VIs derived from SPOT satellite data, whereas in the case of high biomass coverage, estimation accuracy decreases with increasing biomass values. Accordingly, percent VC can be estimated with high accuracy anywhere in Iceland, whereas AGB is much more difficult to estimate, particularly for areas with high-AGB variability.

"Hot spot" in the PROP1 gene responsible for combined pituitary hormone deficiency.

As pituitary function depends on the integrity of the hypothalamic-pituitary axis, any defect in the development and organogenesis of this gland may account for a form of combined pituitary hormone deficiency (CPHD). Although pit-1 was 1 of the first factors identified as a cause of CPHD in mice, many other homeodomain and transcription factors have been characterized as being involved in different developmental stages of pituitary gland development, such as prophet of pit-1 (prop-1), P-Lim, ETS-1, and Brn 4. The aims of the present study were first to screen families and patients suffering from different forms of CPHD for PROP1 gene alterations, and second to define possible hot spots and the frequency of the different gene alterations found. Of 73 subjects (36 families) analyzed, we found 35 patients, belonging to 18 unrelated families, with CPHD caused by a PROP1 gene defect. The PROP1 gene alterations included 3 missense mutations, 2 frameshift mutations, and 1 splice site mutation. The 2 reported frameshift mutations could be caused by any 2-bp GA or AG deletion at either the 148-GGA-GGG-153 or 295-CGA-GAG-AGT-303 position. As any combination of a GA or AG deletion yields the same sequencing data, the frameshift mutations were called 149delGA and 296delGA, respectively. All but 1 mutation were located in the PROP1 gene encoding the homeodomain. Importantly, 3 tandem repeats of the dinucleotides GA at location 296-302 in the PROP1 gene represent a hot spot for CPHD. In conclusion, the PROP1 gene seems to be a major candidate gene for CPHD; however, further studies are needed to evaluate other genetic defects involved in pituitary development.

Senescence-related gene expression profiles of rosette leaves of Arabidopsis thaliana: Leaf age versus plant age

Senescence is a form of programmed cell death (PCD) which leads to the death of whole organs, e.g., leaves or flowers, and eventually to the death of entire plants. Like all forms of PCD, senescence is a highly regulated and energy consuming process. Senescence parameters, like protein content, chlorophyll content, expression of photosynthesis-associated genes or senescence-associated genes (SAGs), reveal that senescence occurs in old leaves derived from young plants (6 week old) as well as in young leaves derived from older plants (8 week old), indicating that it is governed by the actual age of the leaves. in order to analyse the differential gene expression profiles during leaf senescence, hybridizations of high-density genome arrays were performed with: i) individual leaves within the rosette of a 6-week-old plant and ii) leaves of the same position within the rosette but harvested from plants of different ages, ranging from 5 to 8 weeks. Cluster and genetree analyses, according to the expression pattern revealed that genes which are up-regulated with respect to the age of the entire plant, showed completely different expression profiles with respect to the age of the individual leaves within one rosette. This was observed even though the actual difference in leaf age was approximately the same. This indicates that gene expression appears to be governed by different parameters: i) the age of the individual leaf and ii) the age and developmental stage of the entire plant.

The role of abscisic acid and water stress in root herbivore-induced leaf resistance

Herbivore-induced systemic resistance occurs in many plants and is commonly assumed to be adaptive. The mechanisms triggered by leaf-herbivores that lead to systemic resistance are largely understood, but it remains unknown how and why root herbivory also increases resistance in leaves. To resolve this, we investigated the mechanism by which the root herbivore Diabrotica virgifera induces resistance against lepidopteran herbivores in the leaves of Zea mays. Diabrotica virgifera infested plants suffered less aboveground herbivory in the field and showed reduced growth of Spodoptera littoralis caterpillars in the laboratory. Root herbivory did not lead to a jasmonate-dependent response in the leaves, but specifically triggered water loss and abscisic acid (ABA) accumulation. The induction of ABA by itself was partly responsible for the induction of leaf defenses, but not for the resistance against S. littoralis. Root-herbivore induced hydraulic changes in the leaves, however, were crucial for the increase in insect resistance. We conclude that the induced leaf resistance after root feeding is the result of hydraulic changes, which reduce the quality of the leaves for chewing herbivores. This finding calls into question whether root-herbivore induced leaf-resistance is an evolved response. © The Authors (2010). Journal compilation © New Phytologist Trust (2010).

Microsurgical and laser ablation analysis of leaf positioning and dorsoventral patterning in tomato

Leaves are arranged according to regular patterns, a phenomenon referred to as phyllotaxis. Important determinants of phyllotaxis are the divergence angle between successive leaves, and the size of the leaves relative to the shoot axis. Young leaf primordia are thought to provide positional information to the meristem, thereby influencing the positioning of new primordia and hence the divergence angle. On the contrary, the meristem signals to the primordia to establish their dorsoventral polarity, which is a prerequisite for the formation of a leaf blade. These concepts originate from classical microsurgical studies carried out between the 1920s and the 1970s. Even though these techniques have been abandoned in favor of genetic analysis, the resulting insights remain a cornerstone of plant developmental biology. Here, we employ new microsurgical techniques to reassess and extend the classical studies on phyllotaxis and leaf polarity. Previous experiments have indicated that the isolation of an incipient primordium by a tangential incision caused a change of divergence angle between the two subsequent primordia, indicating that pre-existing primordia influence further phyllotaxis. Here.. we repeat these experiments and compare them with the results of laser ablation of incipient primordia. Furthermore. we explore to what extent the different pre-existing primordia influence the size and position of new organs. and hence phyllotaxis. We propose that the two youngest primordia (P-1 and P-2) are sufficient for the approximate positioning of the incipient primordium (I-1), and therefore for the perpetuation of the generative spiral, whereas the direct contact neighbours of I-1 (P-2 and P-3) control its delimitation and hence its exact size and position. Finally. we report L I specific cell ablation experiments suggesting that the meristem L-1 layer is essential for the dorsoventral patterning of leaf primordia.

The auxin influx carrier is essential for correct leaf positioning

Auxin is of vital importance in virtually every aspect of plant growth and development, yet, even after almost a century of intense study, major gaps in our knowledge of its synthesis, distribution, perception, and signal transduction remain. One unique property of auxin is its polar transport, which in many well-documented cases is a critical part of its mode of action. Auxin is actively transported through the action of both influx and efflux carriers. Inhibition of polar transport by the efflux inhibitor N-1-naphthylphthalamic acid (NPA) causes a complete cessation of leaf initiation, a defect that can be reversed by local application of the auxin, indole-3-acetic acid (IAA), to the responsive zone of the shoot apical meristem. In this study, we address the role of the auxin influx carrier in the positioning and outgrowth of leaf primordia at the shoot apical meristem of tomato. By using a combination of transport inhibitors and synthetic auxins, we demonstrate that interference with auxin influx has little effect on organ formation as such, but prevents proper localization of leaf primordia. These results suggest the existence of functional auxin concentration gradients in the shoot apical meristem that are actively set up and maintained by the action of efflux and influx carriers. We propose a model in which efflux carriers control auxin delivery to the shoot apical meristem, whereas influx and efflux carriers regulate auxin distribution within the meristem.

The response of four winter wheat (Triticum aestivum L.) varieties to field water deficit: leaf anti-oxidative protection and proteolytic activity

Introduction: Drought is one of the most significant factors that limit plant productivity. Oxidative stress is a secondary event in many unfavorable environmental conditions. Intracellular proteases have a role in the metabolism reorganisation and nutrient remobilization under stress. In order to under stand the relative significance of oxidative stress and proteolysis in the yield reduction under drought, four varieties of Triticum aestivum L. with different field drought resistance were examined. Methods: A two-year field experiment was conducted. Analyses were performed on the upper most leaf of control plants and plants under water deficitat the stages most critical for yield reduction under drought (from jointing till milk ripeness). Leaf water deficit and electrolyte leakage, malondyaldehyde level, activities and isoenzymes of superoxide dismutase, catalase and peroxidase, leaf protein content and proteolytic activity were studied. Yield components were analyzed. Results: A general trend of increasing the membrane in stability and accumulation of lipid hydroperoxides was observed with some differences among varieties, especially under drought. The anti-oxidative enzyme activities were progressively enhanced, as well as the azocaseinolytic activities. The leaf protein content decreased under drought at the last phase. Differences among varieties were observed in the parameters under study. They were compared to yield components` reduction under water deprivation.

Om den af Keiser Julianus med forenede Jødernes og Hedningenes Kraefer til Spot for Christus og de Christne begyndte Tempelbygning i Jerusalem hvorledes samme ved Hvirvelvind, Lynild, Jordskielv og Ild-Udbrud af Jorden paa en mirakulos Maade blev standset og gandske forhindret : bedraget som et af de alleruimodsigeligste of kraftigste Beviser for den christelige Religions Sandhed...

af [Esaias] Fleischer

On the stratigraphic integrity of leaf-wax biomarkers in loess paleosols

Paleoenvironmental and paleoclimate reconstructions based on molecular proxies, such as those derived from leaf-wax biomarkers, in loess-paleosol sequences represent a promising line of investigation in Quaternary research. The main premise of such reconstructions is the synsedimentary deposition of biomarkers and dust, which has become a debated subject in recent years. This study uses two independent approaches to test the stratigraphic integrity of leaf-wax biomarkers: (i) long-chain n-alkanes and fatty acids are quantified in two sediment-depth profiles in glacial till on the Swiss Plateau, consisting of a Holocene topsoil and the underlying B and C horizons. Since glacial sediments are initially very poor in organic matter, significant amounts of leaf-wax biomarkers in the B and C horizons of those profiles would reflect postsedimentary root-derived or microbial contributions. (ii) Compound-specific radiocarbon measurements are conducted on n-alkanes and n-alkanoic (fatty) acids from several depth intervals in the loess section "Crvenka", Serbia, and the results are compared to independent estimates of sediment age. We find extremely low concentrations of plant-wax n-alkanes and fatty acids in the B and C horizons below the topsoils in the sediment profiles. Moreover, compound-specific radiocarbon analysis yields plant-wax 14C ages that agree well with published luminescence ages and stratigraphy of the Serbian loess deposit. Both approaches confirm that postsedimentary, root-derived or microbial contributions are negligible in the two investigated systems. The good agreement between the ages of odd and even homologues also indicates that reworking and incorporation of fossil leaf waxes is not particularly relevant either.