Understanding the Molecular Basis of Differential Growth during Apical Hook Development

Plants’ adaptation to their environment often involves change in development, which in many cases involves the establishment of differential growth rates across organs, for instance during phototropic and gravitropic responses. A striking example of differential growth is the formation of the apical hook, a structure that forms to protect the apical meristem as seedlings penetrate through soil. Coordination of differential growth across tissues is a multilayered process involving the combined effect of spatiotemporally controlled events such as gene expression, biosynthesis of proteins and polymers, transport and incorporation of biosynthetic products to their sites of participation, regulation of expansion driven by vacuolar turgor and control of cell mechanical properties via cell wall modifications. This thesis addresses mechanisms that underlie differential growth, using the apical hook as a model. Particularly, this work focuses on the role of two distinct but interrelated processes; transport of components to the cell surface, and regulation of composition of components at the cell surface in apical hook development. This work demonstrates that secretion of different auxin carriers follow distinct routes from the trans-Golgi network (TGN) to the plasma membrane, where delivery of AUX1 but not PIN3 relies the TGN-localized protein ECHIDNA (ECH). Data show that the ECH-dependent secretory pathway is essential for ethylene-mediated differential growth of the apical hook in Arabidopsis. Moreover, this work investigates the mechanism by which ECH operates, and shows that ECH is required for the localization of the GTPase ARF1 and its activator GEFs BIG1-4, which are key components of a vesicle formation machinery at the TGN. ARF1 members and BIG1-4 are, like ECH, required for AUX1 delivery to the PM and for ethylene-mediated hook development. Finally, the thesis explores the role of the cell wall in differential growth, particularly, that of homogalacturonan pectin and its modification by methylesterification. This thesis demonstrates that differential cell elongation during hook development relies on establishing asymmetric cell wall mechanical properties across the hypocotyl via pectin methylesterification modifications in an auxin-dependent manner, and that a mechanochemical component provides feedback to the auxin machinery. Taken together, this thesis demonstrates the multilayered regulation of growth asymmetry which facilitates shape generation

Curing the sick and creating supermen – How relaxation in flotation tanks is advertised on the Internet

AbstractIntroductionFlotation-REST (Restricted Environmental Stimulation Technique) is a complementary and alternative medicine therapy with evidence-based beneficial effects like pain and stress reduction. During flotation-REST a person is lying in a supine position inside a quiet and dark tank, filled with salt water maintained at skin temperature. The water is high in buoyancy, which makes it possible to float comfortably on the back. The method induces deep relaxation through minimization of sensory input. Contemporary scientific findings about beneficial effects resulting from floating have increased the number of private owned floating centers. The aim of this study was to investigate how these centers advertise the benefits of flotation to the public and compare these claims with published scientific evidence.MethodThe Google search engine was used to localize web-sites hosting private floating center entrepreneurs. Described effects resulting from floating on these sites were systematically gathered and analyzed thematically. In addition, advertisements were compared to scientific studies on flotation-REST.ResultsThe analysis resulted in five overarching themes: (1) Physiological changes, (2) Alleviation of medical conditions, (3) Relaxation, (4) Personal growth and enhancement, and (5) Altered states of consciousness. Advertisements seemed to target four different interest groups: the inner explorers; the sick; the supermen; and the stressed out. Various effects of flotation were highlighted for the different groups and some limited scientific evidence identified.ConclusionsAlthough the advertisements described many evidence-based effects resulting from floating, information tended to be exaggerated, could be misleading to consumers, and was not always substantiated by published scientific studies

The fate of the missing spores

It is well-known that many species with small diaspores can disperse far during extended temporal scales (many years). However, studies on short temporal scales usually only cover short distances (in, e.g., bryophytes up to 15 m). By using a novel experimental design, studying the realized dispersal, we extend this range by almost two orders of magnitude. We recorded establishment of the fast-growing moss Discelium nudum on introduced suitable substrates, placed around a translocated, sporulating mother colony. Around 2,000 pots with acidic clay were placed at different distances between 5 m and 600 m, in four directions, on a raised bog, with increased pot numbers with distance. The experiment was set up in April-May and the realized dispersal (number of colonized pots) was recorded in September. Close to the mother colony (up to 10 m), the mean colonization rates (ratio of colonized pots) exceeded 50%. At distances between 10 and 50 m colonization dropped sharply, but beyond 50 m the mean colonization rates stabilized and hardly changed (1-3%). The estimated density of spores causing establishments at the further distances (2-6 spores/m2) was realistic when compared to the estimated spore output from the central colonies. Our study supports calculations from earlier studies, limited to short distances, that a majority of the spores disperse beyond the nearest vicinity of a source. The even colonization pattern at further distances raises interesting questions about under what conditions spores are transported and deposited. However, it is clear that regular establishment is likely at the km-scale for this and many other species with similar spore output and dispersal mechanism

Mechanochemical feedback mediates tissue bending required for seedling emergence

Tissue bending is vital to plant development, as exemplified by apical hook formation during seedling emergence by bending of the hypocotyl. How tissue bending is coordinated during development remains poorly understood, especially in plants where cells are attached via rigid cell walls. Asymmetric distribution of the plant hormone auxin underlies differential cell elongation during apical hook formation. Yet the underlying mechanism remains unclear. Here, we demonstrate spatial correlation between asymmetric auxin distribution, methylesterified homogalacturonan (HG) pectin, and mechanical properties of the epidermal layer of the hypocotyl in Arabidopsis. Genetic and cell biological approaches show that this mechanochemical asymmetry is essential for differential cell elongation. We show that asymmetric auxin distribution underlies differential HG methylesterification, and conversely changes in HG methylesterification impact the auxin response domain. Our results suggest that a positive feedback loop between auxin distribution and HG methylesterification underpins asymmetric cell wall mechanochemical properties to promote tissue bending and seedling emergence

Особенности планирования прибыли в условиях нестабильности цен на материальные ресурсы

Материалы IX Междунар. межвуз. науч.-техн. конф. студентов, магистрантов и аспирантов,Гомель, 28–29 апр. 2009 г

A study of flotation-REST (restricted environmental stimulation therapy) as an insomnia treatment

Objectives: Flotation-REST is a treatment for deep relaxation, where a person is contained in a stimuli-restricted environment and floats in water with high salt content. The aim was to investigate the effects from flotation-REST on people with insomnia diagnosis, as previous studies of flotation-REST have demonstrated some effects on sleep but have limitations regarding sample selections and sleep measures. Material and Methods: Six participants were recruited through an outpatient psychiatry clinic and posters on a university campus. All participants fulfilled criteria for insomnia diagnosis and four fulfilled criteria for major depressive disorder. Using a single case experimental design, daily changes were investigated on sleep logs regarding sleep onset latency (SOL), wake after sleep onset (WASO), total sleep time (TST), and sleep efficiency over the course of 12 sessions consisting of 45 min of flotation-REST. No other treatments were offered simultaneously. Questionnaire data on insomnia severity (the ISI) and depressive severity (the MADRS) were also collected. Results: Three participants improved on their most salient insomnia symptom (long SOL or WASO), and two improved on sleep efficiency. The improvements were maintained 2 months after treatment. Insomnia severity decreased for three patients, whereas depressive severity decreased for five. No changes in TST were found and two patients did not improve on any sleep measure. The two participants who benefitted the most were students in their 20s. Discussion: The results were mixed. Flotation-REST may be beneficial for young adults with sleep-onset insomnia but more research is warranted

Edge influence on vegetation at natural and anthropogenic edges of boreal forests in Canada and Fennoscandia

Although anthropogenic edges are an important consequence of timber harvesting, edges due to natural disturbances or landscape heterogeneity are also common. Forest edges have been well studied in temperate and tropical forests, but less so in less productive, disturbance-adapted boreal forests. We synthesized data on forest vegetation at edges of boreal forests and compared edge influence among edge types (fire, cut, lake/wetland; old vs. young), forest types (broadleaf vs. coniferous) and geographic regions. Our objectives were to quantify vegetation responses at edges of all types and to compare the strength and extent of edge influence among different types of edges and forests. Research was conducted using the same general sampling design in Alberta, Ontario and Quebec in Canada, and in Sweden and Finland. We conducted a meta-analysis for a variety of response variables including forest structure, deadwood abundance, regeneration, understorey abundance and diversity, and non-vascular plant cover. We also determined the magnitude and distance of edge influence (DEI) using randomization tests. Some edge responses (lower tree basal area, tree canopy and bryophyte cover; more logs; higher regeneration) were significant overall across studies. Edge influence on ground vegetation in boreal forests was generally weak, not very extensive (DEI usually < 20 m) and decreased with time. We found more extensive edge influence at natural edges, at younger edges and in broadleaf forests. The comparison among regions revealed weaker edge influence in Fennoscandian forests. Synthesis. Edges created by forest harvesting do not appear to have as strong, extensive or persistent influence on vegetation in boreal as in tropical or temperate forested ecosystems. We attribute this apparent resistance to shorter canopy heights, inherent heterogeneity in boreal forests and their adaptation to frequent natural disturbance. Nevertheless, notable differences between forest structure responses to natural (fire) and anthropogenic (cut) edges raise concerns about biodiversity implications of extensive creation of anthropogenic edges. By highlighting universal responses to edge influence in boreal forests that are significant irrespective of edge or forest type, and those which vary by edge type, we provide a context for the conservation of boreal forests. Edges created by forest harvesting do not appear to have as strong, extensive or persistent influence on vegetation in boreal as in tropical or temperate forested ecosystems. We attribute this apparent resistance to shorter canopy heights, inherent heterogeneity in boreal forests and their adaptation to frequent natural disturbance. Nevertheless, notable differences between forest structure responses to natural (fire) and anthropogenic (cut) edges raise concerns about biodiversity implications of extensive creation of anthropogenic edges. By highlighting universal responses to edge influence in boreal forests that are significant irrespective of edge or forest type, and those which vary by edge type, we provide a context for the conservation of boreal forests

Genetic insight into sick sinus syndrome

Aims. The aim of this study was to use human genetics to investigate the pathogenesis of sick sinus syndrome (SSS) and the role of risk factors in its development. Methods and results. We performed a genome-wide association study of 6469 SSS cases and 1 000 187 controls from deCODE genetics, the Copenhagen Hospital Biobank, UK Biobank, and the HUNT study. Variants at six loci associated with SSS, a reported missense variant in MYH6, known atrial fibrillation (AF)/electrocardiogram variants at PITX2, ZFHX3, TTN/CCDC141, and SCN10A and a low-frequency (MAF = 1.1–1.8%) missense variant, p.Gly62Cys in KRT8 encoding the intermediate filament protein keratin 8. A full genotypic model best described the p.Gly62Cys association (P = 1.6 × 10⁻²⁰), with an odds ratio (OR) of 1.44 for heterozygotes and a disproportionally large OR of 13.99 for homozygotes. All the SSS variants increased the risk of pacemaker implantation. Their association with AF varied and p.Gly62Cys was the only variant not associating with any other arrhythmia or cardiovascular disease. We tested 17 exposure phenotypes in polygenic score (PGS) and Mendelian randomization analyses. Only two associated with the risk of SSS in Mendelian randomization, AF, and lower heart rate, suggesting causality. Powerful PGS analyses provided convincing evidence against causal associations for body mass index, cholesterol, triglycerides, and type 2 diabetes (P > 0.05). Conclusion. We report the associations of variants at six loci with SSS, including a missense variant in KRT8 that confers high risk in homozygotes and points to a mechanism specific to SSS development. Mendelian randomization supports a causal role for AF in the development of SSS

”I Sverige får vi inte slå våra barn, punkt!” - en studie om aga och kulturella betingelser

Idén till denna uppsats kom ifrån den svenska dokumentären Det svenska sveket som sändes på SVT den trettonde maj 2007. Dokumentären behandlade den svenska synen på barnuppfostran ur ett mångkulturellt perspektiv. Svenska studier visar att barn till invandrare löper en högre risk att utsättas för våld i hemmet, samtidigt som samhället idag inte riktar några specifika åtgärder mot denna utsatta grupp. Syftet med vår uppsats var att undersöka hur olika myndigheter som arbetar med barn ser på våld som en kulturell faktor. De frågeställningar som vi främst har arbetat efter är: Ser de sociala aktörer vi kontaktat barnaga som en kulturellt betingad faktor? Kan de sociala aktörer som vi kontaktat skönja skillnader kopplade till kulturella betingelser i avseende på uppfostring, barnsyn och föräldraskap? Vilka konsekvenser innebär det för barn att växa upp med aga, enligt våra intervjupersoner och forskning? Undersökningen är kvalitativ i sin form och baseras på fem intervjuer med professionsföreträdare som i sitt yrke möter barn och familjer. De teorier och perspektiv vi har använt oss av är anknytningsteori, postkolonialt perspektiv och resiliens. I resultat- och analysdelen har vi sedan eftersträvat att koppla samman dessa med citat från våra intervjuer. Våra resultat pekar mot att de sociala aktörer vi intervjuat upplever skillnader i sitt arbete med barn till utomnordiskt födda föräldrar, något som de ofta kopplar till kulturella betingelser. Aktuell forskning visar även att barn med utomnordisk härkomst är särskilt utsatta för aga. När det gäller konsekvenser av att växa upp med aga så visar den forskning vi relaterar till en mängd potentiellt destruktiva konsekvenser

Matching of geometrically and topologically changing meshes

The aim for this thesis is to develop a foundation for a compression system for animated mesh sequences, specifically under dynamic change of mesh geometry and topology. Compression of mesh sequences is of special interest in the game industry and this particular thesis is a part of an ongoing series of projects at EA DICE. One of the primary challenges when creating a mesh compression system is creating a matching bijective subset of the mesh surfaces between two subsequent frames in the animation to guide remeshing of the sequence. This thesis describes a method for producing a bijective set of matching mesh patches between two meshes along with an error metric that captures the quality of the matching in terms of shape similarity and distortion. Theory of mathematical topology and tensor algebra used in methods for high performance scientific digital 3D-image recognition are here adopted to extract similar local features between meshes. Techniques for creating parametrizations of mesh patches are combined with techniques for matching point clouds and deforming mesh geometry under energy minimization in order to produce a matching set of patches. The presented algorithm successfully creates bijective sets of matched patches for subsequent meshes in a sequence as well as measures the error for the matchings. Results show an average matching set size of approximately 25% of the mesh areas over a sequence of meshes. This suggests that the data size of such a sequence could potentially be reduced by 25%