S. cerevisiae have developed the ability to forage for nutrients when presented with conditions of starvation. This dimorphic adaptation is particularly noticeable when yeast are subject to nitrogen depravation and has been termed filamentous growth, as cells form filament-like projections away from the center of the colony. The regulation of this response is under the control of the well-characterized MAPK and cAMP pathways. Previous work showed that Cdk8p phosphorylated a key transcriptional activator of the filamentous response, Ste12p, and subsequently targeted the factor for degradation under conditions of limiting nitrogen. Data presented in this thesis suggests that Cdk8p is regulated by another kinase, Tpk2p. In vitro kinase assays demonstrate that Tpk2p directly phosphorylates Cdk8p on residue Thr37, leading to the destabilization of Cdk8p after growth for 4 hours in SLAD media. Lack of phosphorylation on Thr37 yields a hypo-hypofilamentous phenotype, whereas a phospho-mimic mutant, T37E displays a filamentous hyper-filamentous phenotype.

The North Canterbury tectonic setting involves the southward propagating margin of easterly strike-slip activity intersecting earlier thrust activity propagating east from the Alpine Fault. The resulting tectonics contain a variety of structures caused by the way these patterns overlap, creating complexities on the regional and individual feature scale. An unpublished map by Jongens et al. (1999) shows the Ashley-Loburn Fault System crossing the plains from the east connected with the Springfield Thrust Fault in the western margins, possibly the southern limit of the east-west trending strikeslip activity. Of note are two hill structures inferred to be affected by this fault system. View Hill to the west, is on the south side of this fault junction, and Starvation Hill further east, was shown lying on the north side of a left stepover restraining bend. During thrust uplift and simple tilting of the View Hill structure, at least two uplift events post date last Pleistocene aggradation accounting for variations in scarp morphology. Broad constraints on fault dip and the age of the displacement surface suggest that slip-rates are in the order of 0.5 mm/year. East from View Hill, the strike-slip fault was originally thought to curve northeast, around the southeast of Starvation Hill. But there is neither evidence of a scarp, nor other clear evidence of surface faulting at Starvation Hill, which poses the question of the extent to which folding may reflect both fault geometry and fault activity. Starvation Hill is a triangular shape, with a series of distinctive smooth, semi-planar surfaces, lapping across both sides of the hill at a range of elevations and gradients. These surfaces are thought to be remnants of old river channels, and are indicative of tilting and upwarping of the hill structure. 3D computer modelling of these surfaces, combined with studies of the cover sequence on the hill, resulted in inferences being drawn as to the location of hinge lines of a dual-hinged anticline and an overview of the tectonic history of the hill. This illustrates the potential to apply topographical and geomorphic studies to the evolution of geometrically complex structures Starvation Hill is interpreted to be the result of two fault-generated folds, one fault trending north, the other, more recent fault, trending east. These two faults are thought to be sequentially developed segments of the original fault zone inferred by Jongens et al. (1999) but with reinterpreted location and mechanism detail. The presence of two faults has resulted in overprinted differential uplift of the structure, which has been significantly degraded, especially in the southwest corner of the hill. The majority of the formation of the northerly trending structure of Starvation Hill is inferred to be pre-Otiran, with uplift of the later east trending structure continuing into the late Pleistocene and Holocene.

Diss. (sammanfattning) Uppsala : Sveriges lantbruksuniv., 2003. / Härtill 4 uppsatser.

Sob o efeito do jejum os animais podem se comportar de várias maneiras e mudar a estratégia de forrageio, se arriscar mais ao se alimentar e responder mais rapidamente à presença da presa. Animais ectotérmicos e de metabolismo baixo são bastante afetados pelo jejum, construindo menos abrigos, se alimentando mais e se tornando mais ativos. Escorpiões são predadores predominantemente senta-e-espera mas que podem também deslocar-se em busca de suas presas, especialmente artrópodes. No forrageio, eles dependem de vibrações do substrato e de correntes de ar para localizar e capturar a presa. Esses estímulos são detectados por estruturas como os órgãos em fenda (fina região da cutícula onde ocorrem fendas que detectam vibrações do substrato) e os tricobótrios, que são longas cerdas sensíveis ao deslocamento de ar. Escorpiões são equipados com tricobótrios, mas a função comportamental destas cerdas nesse táxon nunca foi testada experimentalmente. No primeiro capítulo, testamos as hipóteses de que escorpiões em jejum se locomoveriam mais, detectariam mais rapidamente a presa e que a taxa de captura seria maior. Para medir a locomoção, nós dividimos a arena em quadrantes de 11 x 11cm e quantificamos o número de quadrantes utilizados, o número de mudanças de quadrantes e se o animal estava andando ou parado em cada observação. Para quantificar mudanças no limiar de detecção, nós medimos a distância em centímetros e a latência em segundos para detectar a presa. Para medir se houve diferenças na taxa de captura, nós contamos em ambos os grupos o número total de sujeitos experimentais que capturaram o grilo. Nós não encontramos diferenças entre os tratamentos em nenhuma das variáveis medidas. No segundo capítulo, testamos a hipótese de que os tricobótrios são importantes para captura de presas para escorpiões. Previmos que os sujeitos experimentais sem tricobótrios experimentalmente removidos teriam menor sucesso de captura do que os grupos controles (cerda controle removida/controle do procedimento experimental/controle sem manuseio). Previmos ainda que escorpiões sem tricobótrios teriam um maior número de tentativas de captura, que a latência para detecção e para a primeira tentativa de captura seriam maiores e que se orientariam menos vezes para a presa do que animais controle. Colocamos um sujeito experimental e um grilo sem o par de pernas III em uma arena circular com papel sulfite como substrato e filmamos os sujeitos experimentais. Nós não encontramos diferenças nas variáveis medidas entre os grupos comparados. Concluindo, os resultados do primeiro capítulo indicam que talvez o tempo de jejum não tenha sido longo o suficiente para influenciar mudanças no comportamento de forrageio e/ou as diferenças podem aparecer em outros comportamentos não medidos, como o tempo de ingestão. No segundo capítulo, os resultados indicam que os tricobótrios não são essenciais para captura de presas. Dessa forma, outras presas e substratos que atenuam vibrações do substrato devem ser considerados em estudos futuros / Under starvation, animals might behave in different ways and change their foraging strategy, become risk-prone while feeding and respond more quickly to the presence of prey. Ectothermic and with low metabolism animals are greatly affected by starvation, building less burrows, feeding more and becoming more active. Scorpions are predominantly sit-and-wait predators but they may also move in search for prey, especially arthropods. While foraging, they rely on substrate borne vibrations and air displacement to detect and capture prey. These stimuli are detect by sensory structures such as slit sense organs, (a thin region on the cuticle that bears slit that detect substrate borne vibration) and trichobothria, which are long setae sensitive to air displacement. Scorpions are equipped with trichobothria, however, the specific behavioral function of these sensilla on this taxa has never been experimentally tested. In the first chapter, we hypothesized that starved scorpions would become more roving, that the threshold to detection would decrease and that the capture rate would increase. To measure locomotion, we divided the arena into squares of 11 x 11 cm and quantified the number of squares used, the number of square changes and if the animal was walking or staying still in each observation. To quantify changes in the detection threshold, we measured the distance in centimeters and latency in seconds to detect the crickets. To measure if there was a difference in capture rate, we counted in both groups the total number of experimental subjects that captured the cricket. We found no differences between treatments in any of the measured variables. In the second chapter, we tested the hypothesis that trichobothria on pedipalps are important for scorpions to capture prey. We predicted that experimental subjects without trichobothria experimentally removed would be less successful in capturing prey than the control groups (control seta removed/control of experimental procedure/no handling control). We also predicted that scorpions without trichobothria would have a higher number of capture attempts, that the latency to detect prey and to the first capture attempt would be higher and the number of times that each scorpion oriented its body towards the prey would be lower. We used an experimental subject and a cricket without the pair of legs III in a circular arena with a printer paper as substrate and then record the experimental subjects. We did not find differences in the measured variables between the two groups. In conclusion, the results of the first chapter indicate that perhaps the starvation period has not been long enough to influence changes on foraging behavior and/or the differences may appear in other behaviors, such as ingestion time. In the second chapter, the results indicate that trichobothria are not essential for capture prey. Thus, other prey and substrates that attenuate substrate borne vibrations should be considered in future studies

The biosynthesis of pyrimidines in Pseudomonas putida was investigated. In this study, pyrimidine requiring mutants were isolated by conventional mutagenesis and enrichment. The strains required exogenously supplied pyrimidines for growth and were found by enzyme assays to be deficient for the product of the pyrB gene encoding the enzyme aspartate transcarbamoylase. None of the intermediates of the pathway could supply the auxotrophic requirement of the strain; only preformed pyrimidines, metabolized via salvage pathways could suffice. Pyrimidine limitation in the mutant caused a slight but significant fifty per cent increase in expression of all the de novo biosynthetic enzymes. Pyrimidine starvation's effect on nucleotide pool levels was examined in the mutant and caused a marked swelling of the purine nucleotide pools.

S. cerevisiae have developed the ability to forage for nutrients when presented with conditions of starvation. This dimorphic adaptation is particularly noticeable when yeast are subject to nitrogen depravation and has been termed filamentous growth, as cells form filament-like projections away from the center of the colony. The regulation of this response is under the control of the well-characterized MAPK and cAMP pathways. Previous work showed that Cdk8p phosphorylated a key transcriptional activator of the filamentous response, Ste12p, and subsequently targeted the factor for degradation under conditions of limiting nitrogen. Data presented in this thesis suggests that Cdk8p is regulated by another kinase, Tpk2p. In vitro kinase assays demonstrate that Tpk2p directly phosphorylates Cdk8p on residue Thr37, leading to the destabilization of Cdk8p after growth for 4 hours in SLAD media. Lack of phosphorylation on Thr37 yields a hypo-hypofilamentous phenotype, whereas a phospho-mimic mutant, T37E displays a filamentous hyper-filamentous phenotype. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate

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京都大学 / 新制・課程博士 / 博士(生命科学) / 甲第23553号 / 生博第464号 / 新制||生||62(附属図書館) / 京都大学大学院生命科学研究科高次生命科学専攻 / (主査)教授 垣塚 彰, 教授 井垣 達吏, 教授 豊島 文子 / 学位規則第4条第1項該当 / Doctor of Philosophy in Life Sciences / Kyoto University / DFAM

This diploma thesis is an experimental study of grease lubrication in a starved elastohydrodynamic lubricated (EHL) contact. Lubricating film thickness is measured with tribological experimental device ball-on-disc using optical interferometry and high speed camera. The experiment is aimed at a comparison of results acquired by ball-on-disc device and full scale axial bearing. In addition, this paper also investigates the influence of number of the rolling elements (overrolling time) on the resulting film thickness.