Environmental control of the Pom1-dependent cell-size regulation pathway in fission yeast

Cells couple their growth and division rate in response to nutrient availability to maintain a constant size. This co-ordination happens either at the G1-S or the G2-M transition of the cell cycle. In the rod-shaped fission yeast, size regulation happens at the G2-M transition prior to mitotic commitment. Recent studies have focused on the role of the DYRK-family protein kinase Pom1, which forms gradients emanating from cell poles and inhibits the mitotic activator kinase Cdr2, present at the cell middle. Pom1 was proposed to inhibit Cdr2 until cells reached a critical size before division. However when and where Pom1 inhibits Cdr2 is not clear as medial Pom1 levels do not change during cell elongation. Here I show that Pom1 gradients are susceptible to environmental changes in glucose. Specifically, upon glucose limitation, Pom1 re-localizes from the poles to the cell sides where it delays mitosis through regulating Cdr2. This re-localization occurs due to microtubule de- stabilization and lateral catastrophes leading to transient deposition of the Pom1 gradient nucleator Tea4 along the cell cortex. As Tea4 localization to cell sides is sufficient to recruit Pom1, this explains the mechanism of Pom1 re-localization. Microtubule destabilization and consequently Tea4 and Pom1 spread depends on the activity of the cAMP-dependent Protein Kinase A (PKA/Pka1), as pka1 mutant cells have stable microtubules and retain polar Tea4 and Pom1 under limited glucose. PKA signaling negatively regulates the microtubule rescue factor CLASP/Cls1, thus reducing its ability to stabilize microtubules. Thus PKA signaling tunes CLASP activity to promote microtubule de-stabilization and Pom1 re-localization upon glucose limitation. I show that the side-localized Pom1 delays mitosis and balances the role of the mitosis promoting, mitogen-associated protein kinase (MAPK) protein Sty1. Thus Pom1 re-localization may serve to buffer cell size upon glucose limitation. -- Afin de maintenir une taille constante, les cellules régulent leur croissance ainsi que leur taux de division selon les nutriments disponibles dans le milieu. Dans la levure fissipare, cette régulation de la taille précède l'engagement mitotique et se fait à la transition entre les phases G2 à M du cycle cellulaire. Des études récentes se sont focalisées sur le rôle de la protéine Pom1, membre de la famille des DYRK kinase. Celle-ci forme un gradient provenant des pôles de la cellule et inhibe l'activateur mitotique Cdr2 présent au centre de la cellule. Le model propose que Pom1 inhibe Cdr2 jusqu'à atteindre une taille critique avant la division. Cependant quand et à quel endroit dans la cellulle Pom1 inhibe Cdr2 n'était pas clair car les niveaux médians de Pom1 ne changent pas au cours de la l'élongation des cellules. Dans cette étude, je montre que les gradients de Pom1 sont sensibles aux changements environnementaux du taux de glucose. Plus spécifiquement, en conditions limitantes de glucose, Pom1 se relocalise des pôles de la cellule pour se distribuer sur les côtés de celle-ci. Par conséquent, un délai d'entrée en mitose est observé dû à l'inhibition Cdr2 par Pom1. Cette délocalisation est due à la déstabilisation des microtubules qui va conduire à une déposition transitoire de Tea4, le nucléateur du gradient de Pom1, tout au long du cortex de la cellule. Comme la localisation de Tea4 sur les côtés de la cellule est suffisante pour recruter la protéine Pom1, ceci explique le mécanisme de relocalisation de celle-ci. La déstabilisation des microtubules et par conséquent la diffusion de Tea4 et Pom1 dépendent de l'activité de la protéine kinase A dépendante de l'AMP cyclique (PKA/Pka1). En absence de pka1, la stabilité des microtubules n'est pas affectée ce qui permet la rétention de Tea4 et Pom1 aux pôles de la cellule même en conditions limitantes de glucose. La signalisation via PKA régule négativement le facteur de sauvetage des microtubules CLASP/Cls1 et permet donc de réduire sa fonction de déstabilisation des microtubules. Ainsi la signalisation via PKA affine l'activité des CLASP pour promouvoir la déstabilisation des microtubules et la relocalisation de Pom1 en conditions limitantes de glucose. Je montre que la localisation sur les côtés retarde l'entrée en mitose et compense l'action de la protéine Sty1, connue pour être une MAPK qui induit l'entrée en mitose. Ainsi, la relocalisation de Pom1 pourrait servir à tamponner la taille de la cellule en condition limitantes de glucose. -- Various cell types in the environment such as bacterial, plant or animal cells have a distinct cellular size. Maintaining a constant cell size is important for fitness in unicellular organisms and for diverse functions in multicellular organisms. Cells regulate their size by coordinating their growth rate to their division rate. This coupling is important otherwise cells would get progressively smaller or larger after each successive cell cycle. In their natural environment cells may face fluctuations in the available nutrient supply. Thus cells have to coordinate their division rate to the variable growth rates shown under different nutrient conditions. During my PhD, I worked with a single-celled rod shaped yeast called the fission yeast. These cells are longer when the nutrient supply is abundant and shorter when the nutrient supply is scarce. A protein that senses changes in the external carbon source (glucose) is called Protein Kinase A (PKA). The rod shape of fission yeast cells is maintained thanks to a structural backbone called the cytoskeleton. One of the components of this backbone is called microtubules, which are small tube like structures spanning the length of the cell. They transport a protein called Tea4, which in turn is important for the proper localization of another protein Pom1 to the cell ends. Pom1 helps to maintain proper shape and size of these rod shaped yeast cells. My thesis work showed that upon reduction in the external nutrient (glucose) levels, microtubules become less stable and show an alteration in their organization. A significant percentage of the microtubules contact the side of the cell instead of touching only the cell tip. This leads to the spreading of the protein Pom1 away from the tips all around the cell periphery. This helps fission yeast cells to maintain the proper size required under these conditions of limited glucose supply. I further showed that the protein PKA regulates microtubule stability and organization and thus Pom1 spreading and maintenance of proper cell size. Thus my work led to the discovery of a novel pathway by which fission yeast cells maintain their size under limited supply of glucose. -- Divers types cellulaires dans l'environnement tels que les bactéries, les plantes ou les cellules animales ont une taille précise. Le maintien d'une taille cellulaire constante est importante pour le fitness des organismes unicellulaire ainsi que pour multiples fonctions dans les organismes multicellulaires. Les cellules régulent leur taille en coordonnant le taux de croissance avec le taux de division. Ce couplage est essentiel sinon les cellules deviendraient progressivement plus petites ou plus grandes après chaque cycle cellulaire. Dans leur habitat naturels les cellules peuvent faire face a des fluctuations dans le taux de nutriment disponible. Les cellules doivent donc coordonner leur taux de division aux taux variables de croissances perçus dans les différentes conditions nutritionnels. Pendant ma thèse, j'ai travaillée sur une levure unicellulaire, en forme de bâtonnet, nommé levure fissipare ou levure de fission. La taille de ces cellules est plus grande quand le taux de nutriments est grand et plus courte quand celui-ci est plus faible. Une protéine qui perçoit les changements dans le taux externe de la source de carbone (glucose) est nommée PKA pour protéine kinase A. La forme en bâtonnet de la cellule est due aux caractères structuraux du cytosquelette. Une composante importante de ce cytosquelette sont les microtubules, dont la structures ressemble à des petit tubes qui vont d'un bout à l'autre de la cellule. Ces microtubules transportent une protéine importante nommée Tea4 qui à leur tour importante pour la bonne localisation d'une autre protéine Pom1 aux extrémités de la cellule. La protéine Pom1 aide à maintenir la taille appropriée des levures fissipares. Mon travail de thèse a montré qu'en présence de taux faible de nutriments (glucose) les microtubules deviennent de moins en moins stables et montrent une désorganisation globale. Un pourcentage significatif des microtubules touche les côtés de la cellule aux lieu d'atteindre uniquement les extrémités. Ceci a pour conséquence une diffusion de Pom1 tout au long du cortex de la cellule. Ceci aide les levures fissipares à maintenir la taille appropriée pendant ce stress nutritionnel. De plus, je montre que PKA régule la stabilité et l'organisation des microtubules et par conséquent la diffusion de Pom1 et le maintien d'une taille constante. En conclusion, mon travail a conduit à la découverte d'un nouveau mécanisme par lequel la levure fissipare maintient sa taille dans des conditions limitantes en glucose.

Business Models of Packaging Machinery Manufacturers – Case Study

The goal of the study was to find a proper frame to understand business models and study business models of the chosen companies in packaging machinery manufacturing. Good practices and tips are searched from business models which have helped companies to success. Packaging industry’s future is also examined in front of different kinds of changes and the influence which they have on machinery manufacturer’s business models. In the theory part business models’ history and the best frame suitable for this study are presented. The chosen case companies have been discussed according to the frame, and they have been compared to each other to point out the differences. The good practices noticed in companies and according to information from other sources, new business model has been constructed including things that should be noticed while constructing a new business model. The information sources of this study where interviews, annual reports, companies presentations and web pages. The type of study was an interpretative case study.

Defeitos superficiais em 2H-WS2 observados por microscopia de tunelamento

Scanning tunnelling microscopy (STM) was used to characterise the basal surface of fresh cleaved crystals of 2H-WS2. Although no impurity or stacking faults could be detected by X-ray diffraction, STM images obtained with negative bias voltage showed two kinds of defects. These defects were attributed to an iodine derivative used as transport agent. In a flat surface free of defects, an image with atomic resolution was achieved with sulphur distances and angles as expected for hexagonal symmetry of 2H-WS2.

Eletrodos artesanais para voltametria

This paper describes the construction and performance of homemade electrodes for voltammetric purpose using cheap materials, like pipette tips and asbestos fiber. A good cost-to-benefit relation makes this devices specially designed for student use, expecting to improve the broadcasting of electroanalytical methods in Brazilian schools.

Studies of Eu- and Yb-induced Reconstructions on the Si(100) Surface

This thesis presents experimental studies of rare earth (RE) metal induced structures on Si(100) surfaces. Two divalent RE metal adsorbates, Eu and Yb, are investigated on nominally flat Si(100) and on vicinal, stepped Si(100) substrates. Several experimental methods have been applied, including scanning tunneling microscopy/spectroscopy (STM/STS), low energy electron diffraction (LEED), synchrotron radiation photoelectron spectroscopy (SR-PES), Auger electron spectroscopy (AES), thermal desorption spectroscopy (TDS), and work function change measurements (Δφ). Two stages can be distinguished in the initial growth of the RE/Si interface: the formation of a two-dimensional (2D) adsorbed layer at submonolayer coverage and the growth of a three-dimensional (3D) silicide phase at higher coverage. The 2D phase is studied for both adsorbates in order to discover whether they produce common reconstructions or reconstructions common to the other RE metals. For studies of the 3D phase Yb is chosen due to its ability to crystallize in a hexagonal AlB2 type lattice, which is the structure of RE silicide nanowires, therefore allowing for the possibility of the growth of one-dimensional (1D) wires. It is found that despite their similar electronic configuration, Eu and Yb do not form similar 2D reconstructions on Si(100). Instead, a wealth of 2D structures is observed and atomic models are proposed for the 2×3-type reconstructions. In addition, adsorbate induced modifications on surface morphology and orientational symmetry are observed. The formation of the Yb silicide phase follows the Stranski-Krastanov growth mode. Nanowires with the hexagonal lattice are observed on the flat Si(100) substrate, and moreover, an unexpectedly large variety of growth directions are revealed. On the vicinal substrate the growth of the silicide phase as 3D islands and wires depends drastically on the growth conditions. The conditions under which wires with high aspect ratio and single orientation parallel to the step edges can be formed are demonstrated.

Identificação de microcistina LR ao nível molecular empregando microscopia de força atômica

Microcystins are non-ribosomal peptides that must be detected for its health concern. Here, microcystin LR and its specific antibody were respectively tethered to the substrate and to the tip of an atomic force microscope, after surface functionalization using 3-aminopropyltriethoxysilane and glutaraldehyde. Functionalization was confirmed comparing topographic images taken on bare and modified tips. Force versus distance curves were successfully used to measure the specific antibody-antigen interactions comparing with a control in which microcystin was initially blocked by incubation with free antibodies. The results showed unequivocally the specific recognition of MLR, suggesting that this method could be useful for biosensor development.

Desmistificando a proteção por patentes nas universidades

Brazilian universities and research institutions still fail to protect the knowledge and technology produced by their community of students, staff and professors while Intellectual Property (IP) issues along with the role of patents and their strategic management in educational and research institutions remain taboo or misunderstood. The focus of this work was to demystify these subjects, including IP, patents and their requirements, the decision to patent as well as tips for successful patenting. Any student, professor or researcher of an educational or research institution can invent and protect their technology. This paper shows how to make such a patent application.

Detection and transmission of Drechslera avenae from oat seed

Detection, symptoms and symptomless transmission of Drechslera avenae (teleomorph Pyrenophora avenae) from seed were investigated. The present study reported that the D. avenae is frequently found in oat (Avena sativa) seed in Argentina. The prevalence of the seed lot infected was 54%. The incidence of seeds infected by D. avenae in the various seed lots from different regions ranged from 0 to 52% (overall mean of 7%). Besides conidia on conidiophore and immature pseudothecia, D. avenae produced small, spherical to pear-shape picnidia containing tiny conidia, on the seed surface. The pathogen was efficiently transmitted at a rate of 55% from seed to coleoptile tips in symptomless seedlings and at 12.5% to plumules. The importance of the infected seed and its epidemiological role are discussed.

In vitro ectomycorrhiza formation by monokaryotic and dikaryotic isolates of Pisolithus microcarpus in Eucalyptus grandis

The formation of ectomycorrhizas by monokaryotic and dikaryotic isolates of Pisolithus microcarpus (Cooke & Massee) G. Cunn. in Eucalyptus grandis W. Hill ex Maid. was studied by in vitro synthesis in Petri dishes. The formation of ectomycorrhizas was observed for all strains tested. Ectomycorrhizas formed by the monokaryotic strains presented a sheath of hyphae around the roots and a Hartig net limited to the epidermis layer, typical of the angiosperm ectomycorrhizas. Colonization rates, a measure of the number of ectomycorrhizas in relation to the total number of lateral root tips, varied from 23 to 62%. Some monokaryotic strains stimulated the formation of lateral roots, promoting increases of up to 109% above the control. The presence of some of the isolates in the in vitro synthesis medium stimulated the production of thicker lateral root tips. The dimensions of the lateral roots tips and ectomycorrhizas varied from one isolate to the next, indicating a variation in their capacity to provoke morphological changes in the host plant roots. The dikaryotic strain M5M11 presented higher values for lateral root yield, number of ectomycorrhizas, and colonization percentage than the corresponding monokaryotic strains, M5 and M11. This indicated the possibility of selecting compatible performing monokaryotic isolates for the yield of superior dikaryotic strains. The set of monokaryotic strains tested varied greatly in their ability to colonize E. grandis roots and cause secondary metabolism-related morphological changes in roots, providing a wealth of model systems for the study of genetic, physiological, and morphogenetic processes involved in Pisolithus-Eucalyptus ectomycorrhiza formation.

CLONAL PROPAGATION OF NEEM (Azadirachta indica A. Juss.) VIA DIRECT AND INDIRECT IN VITRO REGENERATION

ABSTRACTThe study was conducted with shoot tip explants of neem (Azadirachta indica A. Juss) to identify a viable regenerative process. Shoot tips were obtained from neem embryos cultured alternatingly in DKW medium supplemented with BAP and medium without hormones. Initial shoot development was influenced by cotyledon presence. Basal callus, excised from in vitro stem base, also presented organogenic potential. In some cases, plant lines, obtained from each seed, presented different characteristics. The most common characteristic observed in vitro was callus formation at the stem base. However, the rarest characteristics were stem callus formation and leaf senescence. The regenerated shoot tips were further subculture and rooted on a medium supplemented with IBA so that complete plants could be obtained. The rooted plants were transplanted to a greenhouse and successfully acclimatized. No significant differences in in vivo development were observed between neem plants from callus and from shoot tip propagation.

Spraying systems and traveling speed in the deposit and spectrum of droplets in cotton plant

ABSTRACT Tractor traveling speed can influence the quality of spraying depending on the application technology used. This study aimed to evaluate the droplet spectrum, the deposition and uniformity of spray distribution with different spraying systems and traveling speeds of a self-propelled sprayer in two phenological stages of the cotton plant (B9 and F13). The experimental design was randomized blocks and treatments were three spraying techniques: common flat spray tips; tilted flat jet with air induction, at 120 L ha-1; and rotary atomizer disk, 20 L ha-1, combined with four traveling speeds: 12, 15, 18 and 25 km h-1, with four replications. Spraying deposition was evaluated for both leaf surfaces from the cotton plant apex and base (stage B9) and middle part of the plant (stage F13) with a cupric marker. A laser particle analyzer also assessed the droplet spectrum. The centrifugal power spray system produces more homogeneous droplet spectrum and increased penetration of droplets into the canopy in both phenological stages. Variation on the operating conditions necessary for increased traveling speed negatively influences the pattern of spraying deposits.

En gestaltning av individens erfarenhetsbaserade kunskap inom diabetesvården

The aim of this study is to form the experience-based knowledge of diabetics. The broader intent is to be able to transform this experience-based knowledge as an asset within caring. In this study, a theoretical contact for the empirical data is presented through phronesis, i.e. practical wisdom. Phronesis can be seen as the most suitable form of knowledge to be able to deepen the individual's understanding of experiencebased knowledge. For this research, hermeneutic phenomenology was chosen. Abductive reasoning was the method chosen to approach the data collected through repeated deep interviews with individuals with personal experience of diabetes and the use of insulin pumps. The abductive approach fascilitates a broader interpretation of the primary empirical results via a theory of philosophy of science, such as phronesis, the life-world and the negativity of the experience. The latent message of the empirical data is thereby also additionally highlighted. The synthesis reveals that experience-based knowledge arrives with time, it is personified and praxis-oriented, and before this time, the knowledge and security must be provided by the established care, by people close to the individual or by other external sources. The experience-based knowledge has strenghts and weaknesses. The knowledge is further categorized by the individual's ability to discern and make judgement. Additionally, the experience-based kowledge is a reflecting and action-based knowledge striving to improve the care provided. The experience-based knowledge held by the individual is potentially a great instrument towards improving general knowledge with possible practical applications within the diabetic care. Furthermost, in practical suggestions to fascilitate care. In generally applying knowledge gathered from the individual's experiental point of view, there are inherent risks. These risks could potentially be eliminated through the adoption of a concept where the established care could function as a quality guarantor. A concept taking into account the experiencebased knowledge as a source of information and knowledge in the care for diabetics. Co-created knowledge and understanding is a position found in both self-care and pump-treatment. It is also found through the optimal application of the experience-based knowledge of the individual as well as the knowledge found within the established care, in order to fascilitate well-being. This as expressed by the individual's phronesis-based knowledge.

Unusual bismuth-containing surface layers of III-V compound semiconductors

The understanding and engineering of bismuth (Bi) containing semiconductor surfaces are signi cant in the development of novel semiconductor materials for electronic and optoelectronic devices such as high-e ciency solar cells, lasers and light emitting diodes. For example, a Bi surface layer can be used as a surfactant which oats on a III-V compound-semiconductor surface during the epitaxial growth of IIIV lms. This Bi surfactant layer improves the lm-growth conditions if compared to the growth without the Bi layer. Therefore, detailed knowledge of the properties of the Bi/III-V surfaces is needed. In this thesis, well-de ned surface layers containing Bi have been produced on various III-V semiconductor substrates. The properties of these Bi-induced surfaces have been measured by low-energy electron di raction (LEED), scanning-tunneling microscopy and spectroscopy (STM), and synchrotron-radiation photoelectron spectroscopy. The experimental results have been compared with theoretically calculated results to resolve the atomic structures of the studied surfaces. The main ndings of this research concern the determination of the properties of an unusual Bi-containing (2×1) surface structure, the discovery and characterization of a uniform pattern of Bi nanolines, and the optimization of the preparation conditions for this Bi-nanoline pattern.

Research and development of III-V semiconductor surfaces for improved device interfaces

This thesis is devoted to understanding and improving technologically important III-V compound semiconductor (e.g. GaAs, InAs, and InSb) surfaces and interfaces for devices. The surfaces and interfaces of crystalline III-V materials have a crucial role in the operation of field-effect-transistors (FET) and highefficiency solar-cells, for instance. However, the surfaces are also the most defective part of the semiconductor material and it is essential to decrease the amount of harmful surface or interface defects for the next-generation III-V semiconductor device applications. Any improvement in the crystal ordering at the semiconductor surface reduces the amount of defects and increases the material homogeneity. This is becoming more and more important when the semiconductor device structures decrease to atomic-scale dimensions. Toward that target, the effects of different adsorbates (i.e., Sn, In, and O) on the III-V surface structures and properties have been investigated in this work. Furthermore, novel thin-films have been synthesized, which show beneficial properties regarding the passivation of the reactive III-V surfaces. The work comprises ultra-high-vacuum (UHV) environment for the controlled fabrication of atomically ordered III-V(100) surfaces. The surface sensitive experimental methods [low energy electron diffraction (LEED), scanning tunneling microscopy/spectroscopy (STM/STS), and synchrotron radiation photoelectron spectroscopy (SRPES)] and computational density-functionaltheory (DFT) calculations are utilized for elucidating the atomic and electronic properties of the crucial III-V surfaces. The basic research results are also transferred to actual device tests by fabricating metal-oxide-semiconductor capacitors and utilizing the interface sensitive measurement techniques [capacitance voltage (CV) profiling, and photoluminescence (PL) spectroscopy] for the characterization. This part of the thesis includes the instrumentation of home-made UHV-compatible atomic-layer-deposition (ALD) reactor for growing good quality insulator layers. The results of this thesis elucidate the atomic structures of technologically promising Sn- and In-stabilized III-V compound semiconductor surfaces. It is shown that the Sn adsorbate induces an atomic structure with (1×2)/(1×4) surface symmetry which is characterized by Sn-group III dimers. Furthermore, the stability of peculiar ζa structure is demonstrated for the GaAs(100)-In surface. The beneficial effects of these surface structures regarding the crucial III-V oxide interface are demonstrated. Namely, it is found that it is possible to passivate the III-V surface by a careful atomic-scale engineering of the III-V surface prior to the gate-dielectric deposition. The thin (1×2)/(1×4)-Sn layer is found to catalyze the removal of harmful amorphous III-V oxides. Also, novel crystalline III-V-oxide structures are synthesized and it is shown that these structures improve the device characteristics. The finding of crystalline oxide structures is exploited by solving the atomic structure of InSb(100)(1×2) and elucidating the electronic structure of oxidized InSb(100) for the first time.

LIV I VASSEN : Anvisningar om strandskötsel

Svunna tiders öppna strandområden är numera en sällsynt syn. Betesdjur håller inte längre nere vegetationen vid stränderna, och man slår inte växter som vinterfoder till boskapen. Täta vassruggar har lagt beslag på tidigare betesmarker och man försöker bekämpa den allt mer avlägsna strandlinjen genom muddring. Områden med fritidsbostäder kännetecknas på sina ställen av spikraka grävda farleder för båtar och mellan dem öar av deponeringsmassa bevuxna med vass och björk. Många fåglar som tidigare var mycket vanliga på öppna strandängar har försvunnit, eftersom bara ett fåtal vassfåglar trivs i hög vass. Naturen och landskapet vid Finlands stränder behöver omfattande skötsel för att trenden ska kunna vändas. Näringsflödet till vattendragen måste förhindras och man måste öka avlägsnandet av näringsämnen – såsom skörd av vassruggar. Igenväxta strandområden bör restaureras till strandängar antingen genom slåtter eller bete. Vid muddring av strandområden bör alla följa samma regler, så att strandlandskapet hålls öppet och behåller sin skönhet. Den här guiden tar upp strandskötsel på ett mångsidigt sätt och ger praktiska tips om de lämpligaste skötselmetoderna. Vi bör värna om Finlands strandlandskap – tillsammans.