Doctor of Philosophy

dissertationType I diabetes is caused by selective loss of insulin-producing β-cells. Identifying and activating an endogenous source of new β-cells could be used to replenish those lost in this disease. The nature and existence of an adult pancreatic stem/progenitor cell population, however, is still controversial. Circumstantial evidence indicates that islet cells arise from embryonic ductal cells. In contrast, the majority of adult islet cells appear to regenerate via self-renewal during postnatal expansion and adult homeostasis. That ducts could also give rise to new beta-cells in the adult (neogenesis) was recently suggested in the context of pancreatic ductal ligation (PDL) injury. The Notch signaling pathway inhibits islet development and promotes progenitor cell maintenance during early pancreatic organogenesis, acting primarily through its target gene Hes1. While Hes1 is broadly expressed in the embryonic pancreas, only rare Hes1-expressing cells can be found in the adult organ, among mature ducts and centroacinar cells (CACs), the latter of which have been proposed to represent adult progenitors. This thesis aims to test directly the ability of duct cells to generate islet cells, and to determine the biological function of Hes1+ duct cells. For this, we performed lineage tracing and genetic manipulation using two novel Cre-lines, Muc1IC2, which marks exocrine cells, and Hes1C2, which marks Hes1+ cells. Our work has uncovered three major phases in the development of pancreatic islet cells: (i) initially, new islet cells originate from Notchresponsive exocrine cells, (ii) later in embryogenesis, Notch signaling needs to be downiv regulated in exocrine cells for islet neogenesis to proceed and (iii) from birth onwards, islet cells are maintained by replication of pre-existing cells with no detectable influx from neogenesis. Additionally, our findings demonstrated that early Hes1+ cells represent multipotent progenitors and that their immature state is maintained through active Notch signaling. Interestingly, later in development Notch promotes duct specification of Hes1-expressing bipotent exocrine progenitors. In the mature pancreas, Hes1 expression persists in Notch-sensitive centroacinar cells, which act as facultative exocrine-specific progenitor cells. Thus, the research described in this thesis determines the identity of embryonic and adult pancreatic progenitor cells, and demonstrates that these cells utilize Notch signaling for maintenance of their undifferentiated state

Exocrine-to-endocrine differentiation is detectable only prior to birth in the uninjured mouse pancreas

<p>Abstract</p> <p>Background</p> <p>Histological evidence suggests that insulin-producing beta (β)-cells arise in utero from duct-like structures of the fetal exocrine pancreas, and genetic lineage tracing studies indicate that they are maintained in the adult by self-renewal. These studies have not addressed the origin of the new β-cells that arise in large numbers shortly after birth, and contradictory lineage tracing results have been published regarding the differentiation potential of duct cells in this period. We established an independent approach to address this question directly.</p> <p>Results</p> <p>We generated mice in which duct and acinar cells, comprising the exocrine pancreas, can be genetically marked by virtue of their expressing the mucin gene <it>Muc1</it>. Using these mice, we performed time-specific lineage tracing to determine if these cells undergo endocrine transdifferentiation in vivo. We find that <it>Muc1</it>⁺cells do give rise to β-cells and other islet cells in utero, providing formal proof that mature islets arise from embryonic duct structures. From birth onwards, <it>Muc1 </it>lineage-labeled cells are confined to the exocrine compartment, with no detectable contribution to islet cells.</p> <p>Conclusions</p> <p>These results argue against a significant contribution by exocrine transdifferentiation to the normal postnatal expansion and maintenance of β-cell mass. Exocrine transdifferentiation has been proposed to occur during injury and regeneration, and our experimental model is suited to test this hypothesis in vivo.</p

Automatic and unbiased segmentation and quantification of myofibers in skeletal muscle

Skeletal muscle has the remarkable ability to regenerate. However, with age and disease muscle strength and function decline. Myofiber size, which is affected by injury and disease, is a critical measurement to assess muscle health. Here, we test and apply Cellpose, a recently developed deep learning algorithm, to automatically segment myofibers within murine skeletal muscle. We first show that tissue fixation is necessary to preserve cellular structures such as primary cilia, small cellular antennae, and adipocyte lipid droplets. However, fixation generates heterogeneous myofiber labeling, which impedes intensity-based segmentation. We demonstrate that Cellpose efficiently delineates thousands of individual myofibers outlined by a variety of markers, even within fixed tissue with highly uneven myofiber staining. We created a novel ImageJ plugin (LabelsToRois) that allows processing of multiple Cellpose segmentation images in batch. The plugin also contains a semi-automatic erosion function to correct for the area bias introduced by the different stainings, thereby identifying myofibers as accurately as human experts. We successfully applied our segmentation pipeline to uncover myofiber regeneration differences between two different muscle injury models, cardiotoxin and glycerol. Thus, Cellpose combined with LabelsToRois allows for fast, unbiased, and reproducible myofiber quantification for a variety of staining and fixation conditions.Fil: Waisman, Ariel. Fundacion P/la Lucha C/enferm.neurologicas Infancia. Instituto de Neurociencias. - Consejo Nacional de Investigaciones Cientificas y Tecnicas. Oficina de Coordinacion Administrativa Ciudad Universitaria. Instituto de Neurociencias.; ArgentinaFil: Norris, Alessandra. University of Florida; Estados UnidosFil: Elias Costa, Martin. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Kopinke, Daniel. University of Florida; Estados Unido

Anhydride production as an additional mechanism of poly(3-hydroxybutyrate)pyrolysis.

Anhydrides production is newly proposed as an additional pyrolysis mechanism of a biopolymer, poly(3hydroxybutyrate) (PHB). In spite of many suggestions of multiple degradation mechanisms, simple random chain scission by b elimination has been accepted as an exclusive mechanism of the thermal degradation of PHB. However, a wide range of activation energy value of the degradation and the deviation from the random chain scission statistics have suggested the presence of other kinds of mechanism out of the random scission. To confirm other mechanisms out of the random scission, minor pyrolyzates from PHB were characterized with 1H/13C-NMR, Fourier transform infrared spectroscopy, and fast atom bombardment mass spectrometry. As a result, crotonic anhydride and its oligomers were detected as minor products from condensation reactions between carboxyl groups. The anhydrides production must be one reaction out of the conforming process to the random degradation statistics and contribute to the complexity of PHB pyrolysis. An expected thermal degradation pathway of PHB was proposed

Critical evaluation of the 2D-CSIA scheme for distinguishing fuel oxygenate degradation reaction mechanisms

Although the uniform initial hydroxylation of methyl tert-butyl ether (MTBE) and other oxygenates during aerobic biodegradation has already been proven by molecular tools, variations in carbon and hydrogen enrichment factors (εC and εH) have still been associated with different reaction mechanisms (McKelvie et al. Environ. Sci. Technol. 2009, 43, 2793-2799). Here, we present new laboratory-derived εC and εH data on the initial degradation mechanisms of MTBE, ethyl tert-butyl ether (ETBE) and tert-amyl methyl ether (TAME) by chemical oxidation (permanganate, Fenton reagents), acid hydrolysis and aerobic bacteria cultures (species of Aquincola, Methylibium, Gordonia, Mycobacterium, Pseudomonas and Rhodococcus). Plotting of Δδ2H/ Δδ13C data from chemical oxidation and hydrolysis of ethers resulted in slopes (Λ values) of 22 ± 4 and between 6 and 12, respectively. With A. tertiaricarbonis L108, R. zopfii IFP 2005 and Gordonia sp. IFP 2009, εC was low (<|-1|¿) and εH insignificant. Fractionation obtained with P. putida GPo1 was similar to acid hydrolysis and M. austroafricanum JOB5 and R. ruber DSM 7511 displayed Λ values previously only ascribed to anaerobic attack. The fractionation patterns rather correlate with the employment of different P450, AlkB and other monooxygenases, likely catalyzing ether hydroxylation via different transition states. Our data questions the value of 2D-CSIA for a simple distinguishing of oxygenate biotransformation mechanisms, therefore caution and complementary tools are needed for proper interpretation of groundwater plumes at field sites

Applications of Radio-Frequency Heating in Environmental Technology

AbstractDirect dielectric heating with radio-frequency (RF) electromagnetic fields is used to optimize a variety of processes in environmental technology, namely soil remediation by soil vapor extraction or biodegradation, adsorptive-catalytic off-gas treatment, thermal regeneration of drying agents in biogas or natural gas treatment and decontamination and/or drying of brickwork

Extended Ordered Paired Comparison Models with Application to Football Data from German Bundesliga

A general paired comparison model for the evaluation of sports competitions is proposed. It efficiently uses the available information by allowing for ordered response categories and team-specific home advantage effects. Penalized estimation techniques are used to identify clusters of teams that share the same ability. The model is extended to include team-specific explanatory variables. It is shown that regularization techniques allow to identify the contribution of explanatory variables to the success of teams. The usefulness of the methods is demonstrated by investigating the performance and its dependence on the budget for football teams of the German Bundesliga

Study on the (bio)degradation process of bioplastic materials under industrial composting conditions

The objective of this study was to determine the biodegradability of bioplastic materials-sponge cloths-available on the European market. They are labeled as 100 % biodegradable but not certified as compostable. The test was carried out in real composting environment. The project duration was 12 weeks. The emphasis was put on discovering whether the sponge cloths are biodegradable or not. Based on the results, it can be concluded that sponge cloths have decomposed completely (sample C and sample D). Samples A have decomposed but exhibited slower degradation rate. Samples B exhibited the higher degradation rate. The main conclusion from this study is that biodegradation of bioplastics materials strongly depends on both, the environment where they are placed and the chemical nature of the material.O

Kognitiv-psychoedukative Gruppenintervention bei stationären Patienten mit depressiven Erkrankungen – Ergebnisse einer prospektiven Pilotstudie

Background: Psychoeducational interventions that provide disorder-related information in a goal-oriented and structured manner have been integrated in psychiatric and psychotherapeutic approaches. The present cognitive psychoeducational group programme for inpatients with affective disorders is based on a multidimensional functional illness concept which covers aspects of vulnerability, stressors and coping strategies. It covers information about the disorder and its treatment options, building up rewarding activities, cognitive restructuring and relapse prevention. Materials und Methods: This programme was developed and modified at the University of Munich, Department of Psychiatry (LMU). A feasibility study was set up in a follow-up single group design and analyses of variance (ANOVAs) were performed. A total of 231 patients participated in 46 groups. Results: 125 patients evaluated the effectiveness of the programme and its treatment strategies. The group programme was widely accepted among patients that were pharmacologically and psychotherapeutically treated: more than three quarters of the patients rated its contents to be informative, helpful and applicable to everyday living. Conclusions: Inpatients with affective disorders may already benefit from a structured group programme if it takes into account their cognitive and motivational deficits. The group leaders' didactic and psychotherapeutic strategies as well as the patients' exchanging ideas with each other play a central role. In the course of further investigations the programme was differentiated for patients with major depression or bipolar disorders