On the mechanisms underlying neural repression by E(spl)M8 in Drosophila

Notch signaling is an evolutionary conserved pathway that mediates binary cell-fate specification throughout animal development. Through a process termed lateral inhibition, Notch signaling drives two equipotent cells to adopt distinct fates. Binary cell-fate determination has been exceptionally well studied during Drosophila neurogenesis, particularly, in eye and bristle development. In the eye, Notch mediates the selection of R8 photoreceptors from clusters of R8 precursors by antagonizing the activity of the proneural activator Atonal (Ato). In the bristle, Notch drives the selection of the sensory organ precursors (SOP\u27s) from a group of equipotential cells that expressed the proneural activators encoded by the achaete scute complex (ASC). In either case, the conserved basic-Helix-Loop-Helix (bHLH) repressors encoded by the Enhancer of split Complex (E(spl)C) mediate lateral inhibition by antagonizing Ato or ASC. Accumulating evidence indicates that phosphorylation of the E(spl) member M8 by protein kinase CK2 is required for antagonism of Ato/ASC. This modification appears to convert M8 from an autoinhibited state to one that is competent for binding to, and antagonism of Ato or ASC. The work described in this dissertation aims to extend these findings and provide a more detailed understanding of the mechanisms by which M8 mediates neural repression. The studies described in Chapter-2 provide a fundamental reinterpretation of the mechanism by which the m8 allele E(spl)D ablates Ato expression and eye development. Our work indicates that the eye defects of E(spl)D reflect the unique biphasic requirements of Notch during R8 specification, where Notch elicits Ato expression and later elicits E(spl) expression. Specifically, we show that the product of E(spl)D, a truncated protein called M8*, lacks the autoinhibitory domain thereby allowing it to interfere with the first phase of Notch signaling, itself. As a result, M8* impairs expression of Ato to a level that is insufficient to confer the R8 fate. The work of Chapter-3 provides in vivo evidence in support of the autoinhibition model. Using assays for impaired Notch signaling, we show that the C-terminal domain (CtD) of M8 mediates autoinhibition even when expressed as a free peptide. This ability is abolished when the CtD contains a phosphomimetic Asp substitution at the CK2 consensus site, indicating that the 56-residue CtD peptide is sufficient to mediate autoinhibition. Chapter-4 provides genetic evidence that implicates multisite/hierarchical phosphorylation in the regulation of M8 activity. Our studies suggest that CK2 may act as the primary gatekeeper of this cascade of events, which later involve modifications of M8 by MAPK, CK1 and GSK3. Evidence is presented that the MAPK site in M8 is important for neural repression, and that this site is responsive to alteration in EGFR signaling. Multisite phosphorylation may act as a \u27timer\u27 controlling the onset of repression, a regulation that is bypassed by the E(spl)D mutation. The studies in Chapter-5 demonstrate direct genetic interactions between alleles of CK2, Notch and E(spl). The eye, bristle and wing margin defects provide strong evidence that CK2 is a participant in Notch signaling. In Chapter-6, we extend our findings to the bHLH protein Hairy, a member of the HES family. Using in vitro and in vivo assays, we demonstrate that CK2 is required for repression by Hairy as well. Together, the studies described in this dissertation provide novel insights into neural repression, and indicate that posttranslational regulation imposes control over inhibitory Notch signaling

Myeloid Sarcoma: The Other Side of Acute Leukemia

Myeloid sarcomas are extramedullary myeloid masses with associated tissue damage. Myeloid sarcomas usually arise before, during or after diagnosis of acute leukemia, most often AML. Majority of the patients with myeloid sarcoma respond to upfront systemic chemotherapy and sometimes bone marrow transplant, but it is unclear which patients will benefit from which treatments. This is primarily due to the paucity of knowledge on myeloid sarcoma. At present, there are no prognostic biomarkers for myeloid sarcoma, which can help in risk stratification in patients with myeloid sarcoma. Several studies have suggested that myeloid sarcoma is more likely to occur with certain translocations such as CBF and MLL rearrangements. In addition, sequencing analysis has identified several mutations in genes such as FLT3, NPM1, EZH2, and KIT. Nevertheless, there is still lack of knowledge to understand why particular leukemia migrates to the skin and soft tissues and becomes refractory to systemic therapy

Embedded Sensors to Monitor Production of Composites : From Infusion to Curing of Resin

The need for using light-weight and high-strength fibre reinforced polymer in different applications has increased in the past few decades. The ideal product offers excellent mechanical and chemical properties with much lower weight compared to traditionally used metals. Initially, the fibre-reinforced polymers are being produced by trial and error iterations. This causes a very expensive product, with random quality and lack of reproducibility. There is a need to replace trial and error experiments with knowledge-based approaches. Using sensors for in-situ production to monitor the results in a reliable and repeatable way gives a high-quality composite product and optimizes the time and cost of the process. One of the common manufacturing processes of fibre-reinforced polymer composite is resin infusion in dry fabrics. The resin impregnates the fibrous textile through the existence of a pressure gradient in the fibrous mat, which is generated by a vacuum pump or by a resin injection at high pressure. The impregnation of the dry textile is a result of the pressure gradient between resin inlet and venting point in the mold. Therefore, the most relevant measurement to detect the resin front and the changes of resin hydrostatic pressure is measuring the pressure directly inside the laminate. In this study, pressure sensors provide real-time information about the resin front in laminate and the changes of resin hydrostatic pressure during the infusion. Different pressure sensors and interconnection techniques were examined to minimize the size of the sensing element in the composite. After complete impregnation of the fibres, the curing degree of the resin has to be measured. Microscale interdigital capacitive sensors with a perforated substrate of polyimide are designed and fabricated. The sensors are fabricated on polyimide substrate with a thickness of about 5 micrometers. The polyimide is thermally stable up to 450 degree celsius. Therefore, the sensor can be used for a variety of processes even with high-temperature curing requirements. They have a volume of around 0.1 mm3. The miniaturized dimensions of the sensor enables it to remain in the composite product with the negligible diminishing of mechanical properties. The metallization of the sensor is insulated with metal oxide built up from the metallization itself. This insulation layer enables measurement in electrically conductive carbon fibres. The sensors will remain inside the composite material for structural health monitoring during the life-time of composite. Ideally, the sensors for online process monitoring of composites should be made of the identical fibres or resin in that composite. This will eliminate the wound effect in the host material. To obtain sensorial material, a high-performance resin for aerospace application, type RTM6, is mixed with different plasticizers. The cured mixture of the resin is thin and flexible. An interdigital comb structure is screen-printed on the newly developed substrate. The curing degree of the RTM6 resin in glass and carbon fibres is measured by screen-printed planar interdigital sensor on flexible RTM6. Having sensors for online process monitoring is important for industry 4.0 to autonomously produce fibre reinforced composites in a so-called smart factory . Both, pressure sensors and interdigital capacitive sensors in this thesis can be used for online process monitoring. They will provide a knowledge-based approach for high-quality and low-cost products

Blast shock-wave characterization in experimental shock tubes

Blast-induced traumatic brain injuries have affected U.S. soldiers deployed for extended periods in the gulf and Afghanistan wars. To identify the biomechanical and biochemical mechanisms of injury, critical in the identification of diagnostic and therapeutic tools, compressed gas-driven shock tubes are used by investigators to study shockwave-animal specimen interactions and its biological consequences. However, shock tubes are designed and operated in a variety of geometry with a range of process parameters, and the quality of shock wave characteristics relevant to field conditions and therefore the study of blast-induced traumatic brain injuries suffered by soldiers is affected by those conditions. Lab-to-lab comparison is restricted by these variations, inhibiting data pooling and impeding progress. Shock waves accurately characterized by a validated numerical model can be effective in identifying the relationship between shock characteristics vis-?-vis specific shock tube. In this work, a finite element model was developed and validated with data from carefully designed experiments. It was hypothesized that the shock wave characteristics are governed by the energy source, geometry of the tube and specimen location, both along the length and within the section. Using three specific aims, it was identified that a truncated finite element model is appropriate. It was also shown, while the shock wave replicated the field parameters inside the shock tube, the characteristics outside the tube was complex and as affected by vortex tube and jet winds. Therefore, it was determined that this location may not be suitable for replication relevant to the mild TBI problem. It was also determined that shape, size, and location of occlusion increases with the ratio of obstruction to shock tube cross-section

Effect of endplate on the blast wave profile in a compressed gas shock tube

Blast related brain injuries are commonly encountered in the recent wars of Iraq and Afghanistan increased use of improvised explosive devices (IEDs). An estimated 20% of veterans returning from these operations have suffered traumatic brain injuries (TBI). The mechanisms and long-term effects of the injury are not fully understood, and extensive research effort is being focused toward identifying the mechanisms of primary blast injury. When a pure shock-blast wave encounters a subject, in the absence of shrapnel, casing or gaseous products, the loading is termed as primary blast loading, and its effects can be studied using shock tubes. The wave profile of the shock-blast wave produced by the shock tube is characterized by blast overpressure, positive time duration, and impulse. Evolution of the blast wave profiles along the length of the compression driven gas shock tube is studied using experiments and numerical simulations. It is important to identify Shock-blast wave parameters (SWPs), and understand the relationships between the shock tube adjustable parameters (SAPs) and SWPs, in order to control blast wave profiles. In this thesis work, the position of the end plate is the SAP that is specifically studied. Since the shock tube has an open-ended configuration, in order to contain the shock-blast wave and obtain an acceptable Friedlander curve, an endplate was attached to the open end, as a design concept. It was found that the endplate to shock tube end distance affected the shock wave profile. In this research work, the endplate distances were varied and the evolution of shock profile was measured. It was found that at 4 inches distance from the open end, in the current configuration of the shock tube, the desired Friedlander curve was achieved. At other distances, secondary reflection effects were noticed

Analyse Genotypique De La Contribution De La Matiere Assimilée Du Pedoncule Dans Le Remplissage Du Grain Chez Le Ble Dur (Triticum Durum D.E.S.F.)

In a part of study on morpho-physiological characterization in durum wheat; we were interested in quantifying the stem dry matter produced after anthesis and its contribution in the grain filling. When the climatic conditions are unfavorable ; the photosynthetic activity of the post-anthesis is reduced. The plant then uses the assimilates stored in the stem to increase its filling rate of grain. Thus, the behavior of four varieties of durum wheat is analyzed in the field using different parameters: (i) relative water content (RWC) of the flag leaf (ii) dry weight development of the grains (iii) peduncle assimilated dry matter contribution in the grain filling. The leaf water status, appreciated by measuring the RWC, is an indicator of the photosynthetic apparatus functioning. The measured values showed a significant difference between two agricultural companions. The results also showed a genotypic difference in the dry matter accumulation in the grains, mainly related to its filling speed. The accumulation of assimilates in the peduncle during the days following flowering, constitutes an advantage of reserves in dry matter before installation of water deficit. Indeed, it affects production by decreasing the photosynthetic activity. In conclusion, this experiment has highlighted two types of grain yield elaboration of cultivated wheat in the post-anthesis water deficit conditions