Abscisic acid and assimilate partitioning during seed development

This thesis describes the influence of abscisic acid (ABA) on the transport of assimilates to seeds and the deposition of reserves in seeds. It is well-known from literature that ABA accumulates in seeds during development, and that ABA concentrations in seeds correlate rather well with seed size and seed growth rates. However, since ABA is at least partly synthesized in the leaves and transported to the seeds via the phloem, a correlation between ABA levels and growth rate can easily be explained as the result of the combined transport of ABA and assimilates. Reports about the effect of applied ABA on transport of assimilates to seeds are contradictory (Table 1.I). Moreover, application of ABA has several disadvantages: the application technique itself may cause artefacts, and the results are difficult to interpret since the endogenous ABA level after application depends on penetration, transport and metabolism in the tissue. For these reasons, we have chosen for a different approach, viz . the use of hormone mutants. Two species were used: Pisum sativum and Arabidopsis thaliana .Growth and development of the ABA-deficient ' wilty ' mutant of pea is described in detail (Chapter 2). A non-wilty isogenic line was obtained after six successive backcrosses of the mutant with a closely approximating line. The plants were grown at conditions of high relative humidity and cultured on hydroponics, since leaves of ABA-deficient plants fail to accumulate ABA at drought stress and consequently do not close their stomata- For the same reason, mutant leaves have a higher dry matter content than wild-type leaves. The mutant grew slower and especially root growth was reduced; this resulted in a considerably larger shoot/root ratio. Similar effects have been found in ABA-deficient mutants of several other species. This root-growth promotive effect of ABA can be explained as a measure to prevent an undesirable water status of the leaves by increasing the volume of soil explored under dry conditions.ABA-deficient plants had fewer and smaller seeds than wild-type plants, but since the mutants plants themselves were also smaller, the weight ratio of reproductive to vegetative parts was similar in both lines. The seeds of mutant plants contained about five times less ABA than wild-type seeds. It was concluded that the lower growth rate of both vegetative and reproductive parts was not directly caused by the lower ABA content of these organs, but by disturbed water relations.One of the reasons to choose the pea mutant was that transport of assimilates to legume seeds can be studied by the empty-seed-coat technique. After removal of a part of the pod wall and the seed coat, the embryo is replaced by a buffer, while leaving most of the maternal tissue intact. This buffer receives assimilates from the seed-coat and is regularly analysed for the presence of sucrose. The rate of sucrose efflux calculated from the seed-coat into the medium is assumed to be a measure for phloem import, especially during the period of near-constant sucrose release (4-10 hours after the start of the experiment). The effect of ABA on sucrose release was studied by applying various ABA concentrations to the buffer (Figure 3. 1) and expressing the amount of sucrose released into these buffers relative to the amount present in a control seed-coat (a surgically modified seed-coat containing buffer without ABA). It was shown that hardly any ABA leaked from one seed-coat to another. The experiments were performed with both wildtype and ABA-deficient plants, either or not at source-limited conditions, since it was assumed that a possible effect of ABA might be more pronounced in ABA-deficient plants and at source-limited conditions. Source-limiting indeed caused a reduction of the sucrose release- rate. However, no effect of ABA on sucrose release could be discerned, irrespective of the experimental conditions.Another advantage of the use of mutants is the possibility to study competition between genetically different seeds, for the same source of assimilates (Figure 1.3). In pea, this was achieved by crossing an ABA-deficient mother plant with pollen from plants that were heterozygous for this trait. Chapter 4 describes experiments on ABA-deficient pea plants bearing pods with both ABA-deficient and ABA-containing seeds in the same pod. Seeds in the same pod usually have the same growth rate. In these pods, the growth rate of the seeds was determined by measuring the diameter of the seeds with a pair of callipers. In a control experiment it was shown that these manipulations (opening of the pod and measuring the seeds) did not disturb the normal growth pattern of the seeds. No effect of the genotype on the growth rate of the seeds was detected.Similar studies were performed with Arabidopsis mutants (Chapter 5). In one series of experiments, successive flowers of a recombinant of an ABA-deficient and an ABA-insensitive mutant (aba,abi3) were alternatingly pollinated with pollen from either wildtype or double-mutant plants. In another series of experiments, a double-mutant that was both ABA-deficient and starchless was used as a mother plant; the amount of available assimilates in these plants was reduced by decreasing the light intensity. The growth rate of the seeds was determined by exposing the mother plants to radiolabelled CO 2 and detecting the amount of radioactivity in the seeds. The weight of the seeds of these crosses was determined on a high-precision balance. In these experiments, again no significant influence of the genotype on either the import of radioactivity or the weight of the seeds could be detected.The possible effect of ABA on the deposition of reserve material in seeds was studied with some Arabidopsis mutants. Arabidopsis is a crucifer and its seeds initially accumulate starch which is degraded and converted to lipids during seed maturation. Seeds of the ABA-deficient (aba) and the ABA-insensitive (abi3) mutant and their recombinant (aba,abi3) were collected during development and their lipid and carbohydrate composition was analysed and compared with wild-type seeds. The maximum dry and fresh weight of the seeds was not influenced by the genotype. All mutants had considerably reduced levels of eicosenoic acid (20: 1) in the triacylglycerol fraction as compared to wild- type seeds; it is concluded that ABA is involved in the regulation of elongation of fatty acids. The total amount of neutral lipids in seeds of the single mutants was similar to that in wild-type seeds (about 30-35 % on a dry weight basis), but doublemutant seeds contained only half this amount. On the other hand, double-mutant seeds had elevated levels of starch and soluble sugars. Apparently, the blockade in lipid synthesis in these mutants is so strong that it results in starch accumulation and finally in accumulation of soluble sugars. It is concluded that both the presence of ABA and the sensitivity to ABA are required for normal acyl-chain elongation and lipid accumulation; the absence of both factors results in a higher proportion of the imported assimilates being stored as carbohydrates.From the above-mentioned experiments, it was concluded that ABA has no major influence on the long-distance transport of assimilates, at least not in the species Pisum sativum and Arabidopsis thaliana. However, ABA appears to be involved in the distribution of assimilates over the various types of storage material during seed development

Characteristics of daily life gait in fall and non fall-prone stroke survivors and controls

BACKGROUND: Falls in stroke survivors can lead to serious injuries and medical costs. Fall risk in older adults can be predicted based on gait characteristics measured in daily life. Given the different gait patterns that stroke survivors exhibit it is unclear whether a similar fall-prediction model could be used in this group. Therefore the main purpose of this study was to examine whether fall-prediction models that have been used in older adults can also be used in a population of stroke survivors, or if modifications are needed, either in the cut-off values of such models, or in the gait characteristics of interest. METHODS: This study investigated gait characteristics by assessing accelerations of the lower back measured during seven consecutive days in 31 non fall-prone stroke survivors, 25 fall-prone stroke survivors, 20 neurologically intact fall-prone older adults and 30 non fall-prone older adults. We created a binary logistic regression model to assess the ability of predicting falls for each gait characteristic. We included health status and the interaction between health status (stroke survivors versus older adults) and gait characteristic in the model. RESULTS: We found four significant interactions between gait characteristics and health status. Furthermore we found another four gait characteristics that had similar predictive capacity in both stroke survivors and older adults. CONCLUSION: The interactions between gait characteristics and health status indicate that gait characteristics are differently associated with fall history between stroke survivors and older adults. Thus specific models are needed to predict fall risk in stroke survivors

The effects of knee arthroplaste on walking speed. A meta-analysis.

Background: Patients with knee osteoarthritis patients have problems with walking, and tend to walk slower. An important aim of knee arthroplasty is functional recovery, which should include a post-operative increase in walking speed. Still, there are several problems with measuring walking speed in groups of knee osteoarthritis patients. Nevertheless, test-retest reliability of walking speed measurements is high, and when the same investigators monitor the same subjects, it should be possible to assess the walking speed effects of knee arthroplasty. The present study reports a meta-analysis of these effects. Methods. A total of 16 independent pre-post arthroplasty comparisons of walking speed were identified through MEDLINE, Web of Science, and PEDro, in 12 papers, involving 419 patients. Results: For 0.5-5 months post-operatively, heterogeneity was too large to obtain a valid estimate of the overall effect-size. For 6-12 and 13-60 months post-operatively, heterogeneity was absent, low, or moderate (depending on estimated pre-post correlations). During these periods, subjects walked on average 0.8 standard-deviations faster than pre-operatively, which is a large effect. Meta-regression analysis revealed significant effects of time and time squared, suggesting initial improvement followed by decline. Conclusion: This meta-analysis revealed a large effect of arthroplasty on walking speed 6-60 months post-operatively. For the first 0.5-5 months, heterogeneity of effect-sizes precluded a valid estimate of short-term effects. Hence, patients may expect a considerable improvement of their walking speed, which, however, may take several months to occur. Meta-regression analysis suggested a small decline from 13 months post-operatively onwards. © 2012 Abbasi-Bafghi et al; BioMed Central Ltd

A Comprehensive Analysis of Ontogeny of Renal Drug Transporters: mRNA Analyses, Quantitative Proteomics, and Localization

Contains fulltext : 209000.pdf (publisher's version ) (Open Access)Human renal membrane transporters play key roles in the disposition of renally cleared drugs and endogenous substrates, but their ontogeny is largely unknown. Using 184 human postmortem frozen renal cortical tissues (preterm newborns to adults) and a subset of 62 tissue samples, we measured the mRNA levels of 11 renal transporters and the transcription factor pregnane X receptor (PXR) with quantitative real-time polymerase chain reaction, and protein abundance of nine transporters using liquid chromatography tandem mass spectrometry selective reaction monitoring, respectively. Expression levels of p-glycoprotein, urate transporter 1, organic anion transporter 1, organic anion transporter 3, and organic cation transporter 2 increased with age. Protein levels of multidrug and toxin extrusion transporter 2-K and breast cancer resistance protein showed no difference from newborns to adults, despite age-related changes in mRNA expression. Multidrug and toxin extrusion transporter 1, glucose transporter 2, multidrug resistance-associated protein 2, multidrug resistance-associated protein 4 (MRP4), and PXR expression levels were stable. Using immunohistochemistry, we found that MRP4 localization in pediatric samples was similar to that in adult samples. Collectively, our study revealed that renal drug transporters exhibited different rates and patterns of maturation, suggesting that renal handling of substrates may change with age

Osteoinductive calcium phosphate with submicron topography as bone graft substitute for maxillary sinus floor augmentation: A translational study

Objectives: The aim of this study was the preclinical and clinical evaluation of osteoinductive calcium phosphate with submicron surface topography as a bone graft substitute for maxillary sinus floor augmentation (MSFA). Material and Methods: A preclinical sheep model of MSFA was used to compare a calcium phosphate with submicron needle-shaped topography (BCPN, MagnetOs Granules, Kuros Biosciences BV) to a calcium phosphate with submicron grain-shaped topography (BCPG) and autologous bone graft (ABG) as controls. Secondly, a 10-patient, prospective, randomized, controlled trial was performed to compare BCPN to ABG in MSFA with two-stage implant placement. Results: The pre-clinical study demonstrated that both BCPN and BCPG were highly biocompatible, supported bony ingrowth with direct bone apposition against the material, and exhibited bone formation as early as 3 weeks post-implantation. However, BCPN demonstrated significantly more bone formation than BCPG at the study endpoint of 12 weeks. Only BCPN reached an equivalent amount of bone formation in the available space and a greater proportion of calcified material (bone + graft material) in the maxillary sinus compared to the “gold standard” ABG after 12 weeks. These results were validated in a small prospective clinical study, in which BCPN was found comparable to ABG in implant stability, bone height, new bone formation in trephine core biopsies, and overall clinical outcome. Conclusion: This translational work demonstrates that osteoinductive calcium phosphates are promising bone graft substitutes for MSFA, whereas their bone-forming potential depends on the design of their surface features. Netherlands Trial Register, NL6436

Water-, milieu- en ruimtecondities vaatplanten : implementatie in Model for Nature Policy - MNP 2.0

Model for Nature Policy (MNP) is ontwikkeld om op nationale of regionale schaal de status van de biodiversiteit te beoordelen. MNP is al geparameteriseerd voor dagvlinders en broedvogels; dit werkdocument bespreekt de toevoeging van vaatplanten. Hiervoor zijn optimale en suboptimale ruimte-, milieu- en watercondities voor plantendoelsoorten bepaald op basis van SynBioSys, neergeschaalde natuurdoeltypenkaart, kritische waarden voor stikstofdepositie en GVGinformatie uit Waternood. We concluderen dat het modelleren van plantensoorten met MNP moeilijker blijkt dan voor de soortgroepen vlinders en vogels; voor 40% van de plantensoorten kon een bruikbaar model gemaakt worden. De huidige analyses laten zien dat voor slechts een beperkt aantal plantensoorten ruimte de beperkende factor is voor duurzaam voorkomen. Milieu- en watercondities doen er meer toe, wat in lijn is met de huidige wetenschappelijke aanpak in veel modellen

The Lateglacial to early Holocene tephrochronological record from Lake Hämelsee, Germany: a key site within the European tephra framework

Here we present the results of a detailed cryptotephra investigation through the Lateglacial to early Holocene transition, from a new sediment core record obtained from Lake Hämelsee, Germany. Two tephra horizons, the Laacher See Tephra (Eifel Volcanic Field) and the Saksunarvatn Ash (Iceland), have been previously described in this partially varved sediment record, indicating the potential of the location as an important Lateglacial tephrochronological site in northwest Europe. We have identified three further tephra horizons, which we correlate to: the ~12.1 ka BP Vedde Ash (Iceland), the ~11 ka BP Ulmener Maar tephra (Eifel Volcanic Field) and the ~10.8 ka BP Askja-S tephra (Iceland). Three additional cryptotephra deposits have been found (locally named HÄM_T1616, HÄM_T1470 and HÄM_T1456-1455), which cannot be correlated to any known eruption at present. Geochemical analysis of the deposits suggests that these cryptotephras most likely have an Icelandic origin. Our discoveries provide age constraints for the new sediment records from Lake Hämelsee and enable direct stratigraphic correlations to be made with other tephra-bearing sites across Europe. The new tephrostratigraphic record, within a partially varved Lateglacial sediment record highlights the importance of Lake Hämelsee as a key site within the European tephra lattice

The ANTARES Optical Beacon System

ANTARES is a neutrino telescope being deployed in the Mediterranean Sea. It consists of a three dimensional array of photomultiplier tubes that can detect the Cherenkov light induced by charged particles produced in the interactions of neutrinos with the surrounding medium. High angular resolution can be achieved, in particular when a muon is produced, provided that the Cherenkov photons are detected with sufficient timing precision. Considerations of the intrinsic time uncertainties stemming from the transit time spread in the photomultiplier tubes and the mechanism of transmission of light in sea water lead to the conclusion that a relative time accuracy of the order of 0.5 ns is desirable. Accordingly, different time calibration systems have been developed for the ANTARES telescope. In this article, a system based on Optical Beacons, a set of external and well-controlled pulsed light sources located throughout the detector, is described. This calibration system takes into account the optical properties of sea water, which is used as the detection volume of the ANTARES telescope. The design, tests, construction and first results of the two types of beacons, LED and laser-based, are presented.Comment: 21 pages, 18 figures, submitted to Nucl. Instr. and Meth. Phys. Res.

An improved method for measuring muon energy using the truncated mean of dE/dx

The measurement of muon energy is critical for many analyses in large Cherenkov detectors, particularly those that involve separating extraterrestrial neutrinos from the atmospheric neutrino background. Muon energy has traditionally been determined by measuring the specific energy loss (dE/dx) along the muon's path and relating the dE/dx to the muon energy. Because high-energy muons (E_mu > 1 TeV) lose energy randomly, the spread in dE/dx values is quite large, leading to a typical energy resolution of 0.29 in log10(E_mu) for a muon observed over a 1 km path length in the IceCube detector. In this paper, we present an improved method that uses a truncated mean and other techniques to determine the muon energy. The muon track is divided into separate segments with individual dE/dx values. The elimination of segments with the highest dE/dx results in an overall dE/dx that is more closely correlated to the muon energy. This method results in an energy resolution of 0.22 in log10(E_mu), which gives a 26% improvement. This technique is applicable to any large water or ice detector and potentially to large scintillator or liquid argon detectors.Comment: 12 pages, 16 figure

Distinctive expansion of potential virulence genes in the genome of the oomycete fish pathogen Saprolegnia parasitica.

Oomycetes in the class Saprolegniomycetidae of the Eukaryotic kingdom Stramenopila have evolved as severe pathogens of amphibians, crustaceans, fish and insects, resulting in major losses in aquaculture and damage to aquatic ecosystems. We have sequenced the 63 Mb genome of the fresh water fish pathogen, Saprolegnia parasitica. Approximately 1/3 of the assembled genome exhibits loss of heterozygosity, indicating an efficient mechanism for revealing new variation. Comparison of S. parasitica with plant pathogenic oomycetes suggests that during evolution the host cellular environment has driven distinct patterns of gene expansion and loss in the genomes of plant and animal pathogens. S. parasitica possesses one of the largest repertoires of proteases (270) among eukaryotes that are deployed in waves at different points during infection as determined from RNA-Seq data. In contrast, despite being capable of living saprotrophically, parasitism has led to loss of inorganic nitrogen and sulfur assimilation pathways, strikingly similar to losses in obligate plant pathogenic oomycetes and fungi. The large gene families that are hallmarks of plant pathogenic oomycetes such as Phytophthora appear to be lacking in S. parasitica, including those encoding RXLR effectors, Crinkler's, and Necrosis Inducing-Like Proteins (NLP). S. parasitica also has a very large kinome of 543 kinases, 10% of which is induced upon infection. Moreover, S. parasitica encodes several genes typical of animals or animal-pathogens and lacking from other oomycetes, including disintegrins and galactose-binding lectins, whose expression and evolutionary origins implicate horizontal gene transfer in the evolution of animal pathogenesis in S. parasitica