196,304 research outputs found
Development of systems for isolation of high-valent nickel complexes and their reactivity
No full textInspired by work published in our group utilizing macrocyclic nitrogen based pyridinophane (N4) and triazacyclononane (tacn) ligands for the isolation and study of high-valent nickel and palladium compounds, chiral variants of these ligands were synthesized in attempts to isolate high-valent organometallic nickel complexes that could play a role in enantioselective crosscoupling reactions. Utilizing readily available chiral pool primary amines, the synthesis of N4 type ligands can be amended to install chirality on the tertiary amines of the ligand, which commonly bind through dative interactions with the metal center in high-valent oxidation states. Furthermore, the synthesis can be expanded to N3 type pyridinophane compounds like N3CBr type ligands, allowing for on-ligand reactivity studies to be conducted. With these ligands in hand, a secondary organometallic nucleophile was synthesized which could allow for the synthesis of organometallic nickel complexes. The reactivity of these complexes was then examined, with hopes that insight into the role of high-valent complexes and the method for stereoinduction in enantioselective cross-coupling reactions could then be better understood.
Furthermore, a synthetic route to novel chiral variants of triazacyclononane ligands was developed based on a ‘crab-like’ synthesis published by the Scarborough group in 2018. This synthesis relies on commercially available alpha-hydroxy acids, and the substituents on the ligand can be varied in a multitude of locations. This ligand synthesis allows for installation of chirality on the methylene backbone of the ligand, which will hopefully result in good chiral projection into the open binding sites of the metal complex. Further efforts to develop reactivity with this system are currently underway.Submission published under a 24 month embargo labeled 'U of I Access', the embargo will last until 2023-08-01The student, Neil Heberer, accepted the attached license on 2021-07-08 at 12:27.The student, Neil Heberer, submitted this Thesis for approval on 2021-07-08 at 12:30.This Thesis was approved for publication on 2021-07-16 at 15:04.DSpace SAF Submission Ingestion Package generated from Vireo submission #16802 on 2022-01-12 at 12:54:00Made available in DSpace on 2022-01-12T22:35:06Z (GMT). No. of bitstreams: 2
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Indoor and HVAC air quality investigation, China Basin - Source characterization, risk assessment and health effects
No full textVEGF-expressing mesenchymal stem cells for improved angiogenesis in regenerative medicine : a bone tissue engineering approach
No full textRapid vascularization of tissue-engineered grafts is a major bottleneck in the development of regenerative medicine approaches. In order to overcome this limitation, we aimed to develop a bone tissue engineering strategy combining cell therapy with pro-angiogenic gene therapy.
Vascular Endothelial Growth Factor (VEGF) is the master regulator of physiological vascular growth and is commonly used as a therapeutic transgene for the induction of angiogenesis. However, uncontrolled and high levels of VEGF expression can lead to aberrant vascular growth. To achieve controlled expression in vivo, a high-throughput flow cytometry-based method has previously been developed in our group. Linking the VEGF cDNA to a cell-surface marker (a truncated version of CD8a) in a bicistronic construct enabled the rapid purification of genetically modified myoblasts secreting a desired VEGF level, using FACS sorting based on the intensity of CD8 expression in each cell. Controlled VEGF expression in skeletal muscle, achieved by implantation of these FACS-purified myoblast populations, induced only normal, stable and functional vascular networks and avoided any aberrant angiogenesis.
The aims of this thesis were to adapt this method to human adipose tissue- and bone marrow-derived mesenchymal stromal/stem cells (ASC and BMSC), and to apply these in a bone tissue engineering approach to increase the vascularization potential of osteogenic grafts.
As MSC gradually loose their regenerative potential during in vitro expansion, we first optimized our genetic engineering method for MSC, so as to enable high transduction efficiency and FACS-purification with minimal in vitro manipulation. Chapter 2 describes the generation of an optimized protocol allowing routine transduction efficiencies of > 90% of primary human ASC and BMSC already during the first plating, as well as flow cytometry purification of transduced cells at the time of the first passage. In addition we demonstrated that it was possible to FACS-purify specific sub-populations of transduced MSC homogeneously producing desired VEGF doses. Neither retroviral vector transduction, FACS-purification, nor the expression of the transgenes VEGF and CD8 impaired MSC proliferation and in vitro differentiation potential. Transgene expression was not lost during in vitro differentiation.
In Chapter 3, proof-of-principle was obtained by applying this platform to a bone tissue engineering approach. Human BMSC, transduced and rapidly FACS-purified to eliminate non-expressing cells, were seeded onto hydroxyapatite granules to generate non-critically sized constructs, and were implanted subcutaneously in nude rats. In vivo vascularization potential was significantly increased in VEGF-expressing BMSC. Although VEGF expression was heterogeneous, no aberrant angiogenesis was observed. Indeed, orderly vascular beds were induced, with flow-conducting arterioles feeding into extensive capillary networks, where metabolic exchanges can take place efficiently. The improvement in vascularization was not diminished by extensive in vitro expansion of the transduced BMSC up to 35 population doublings, showing that genetic modification conferred a stable angiogenic potential. As expected, these expanded BMSC lost their osteogenic potential. However, their sustained capacity to induce vascularization could be useful in other applications, where effective expansion of the vascular bed is required, but not progenitor differentiation, such as in cell-based approaches for therapeutic angiogenesis in peripheral or coronary artery diseases.
By minimizing cell expansion, both naïve and control transduced MSC generated abundant bone tissue in vivo. However, VEGF over-expression specifically caused a strong reduction in bone formation. This correlated with an increased recruitment of TRAP-positive osteoclasts specifically in VEGF-expressing constructs.
These data suggest that VEGF over-expression might impair bone formation by disrupting the balance between bone formation and resorption towards excessive degradation. To fully understand the underlying mechanism, further experiments will be needed.
The method described in chapter 2 provides a general platform to generate populations of genetically modified MSC, expressing specific levels of a therapeutic transgene, already at the time of the first passage. Therefore, it has the potential to be applied in other fields of regenerative medicine, beyond bone tissue engineering. We briefly describe two recently initiated projects, based on the results described in this thesis, which aim at either promoting or inhibiting angiogenesis in order to improve cardiac function after myocardial infarction, or cartilage tissue formation, respectively
Breakdown of C3 complement and IgG in peritonitis exudate-pathophysiological aspects and therapeutic approach
No full textEngineering of cartilage tissue constructs in a 3-dimensional perfusion bioreactor culture system under controlled oxygen tension
No full textThe most relevant results generated in this thesis can be summarized as follow:
· Adult human articular chondrocytes (AHAC) from elderly individuals expanded in culture
medium supplemented with the growth factors TGFβ-1, FGF-2 and PDGF and subsequently
cultured in 3-d pellets had an enhanced chondrogenic capacity when exposed to more
physiological (i.e. 5%) oxygen levels.
· In correlation with the enhanced tissue forming capacity of AHAC from elderly donors under
low oxygen tension, the mRNA expression levels of selective matrix degrading enzymes
were reduced as compared to conventional in vitro oxygen culture condition.
· We developed an integrated bioreactor system, which streamlines within a single device the
phases of perfusion cell seeding and prolonged perfusion culture of cell seeded scaffolds in
vitro.
· The culturing of uniformly seeded adult human articular chondrocytes under direct perfusion,
where cells are continuously exposed to a normoxic range of oxygen levels, can maintain a
uniform distribution of viable cells throughout thick porous scaffolds as compared to
statically cultured constructs.
· The culturing of constructs uniformly seeded with adult human articular chondrocytes under
a more physiological range of oxygen resulted in a higher chondrogenic differentiation as
compared to culture under normoxic levels. Anyhow, this effect was less pronounced as
compared to statically cultured cell constructs or micromass cell pellets, possibly due to the
flow induced shear forces.
· Reduced perfusion flow rates applied to chondrocytes on porous scaffolds significantly
induced more cartilaginous tissue in the presents of low vs. high oxygen levels. However the
effects of low oxygen were not as marked as in pellet culture
The rise of temporary employment in Japan: Legalisation and expansion of a non-regular employment form
No full textThis discussion paper examines the institutionalization process of a non-regular employment form especially focusing on the establishment of the temporary dispatching work (haken) system. The institutionalization process of the haken system can be divided into three periods: delegalisation (1947-86), legalisation (1986-99), and diffusion (1999-). Declining labor strength, the emergence of deregulation bodies, and the changing attitude of the Ministry of Labor (MHLW) characterize the legal developments. Together with the liberalization of private job placement and the expansion of fixed-term contract work, temporary work became an important sources of flexible and skilled labor, and expanded more rapidly than other employment forms in the late 90s. In this development, temporary help firms started to reframe their business as 'personnel services,' and have positioned themselves to replace the traditional firm-internal supply of mobile employees such as shukkô and tenseki with external dispatched employees of temporary help firms. --Japan,temporary work,non-regular employment,labor market,(de-)regulation
Dr. Duane M. Jackson, Morehouse College, July 2011
No full textThis video is a conversation with Dr. Duane M. Jackson. Dr. Jackson talks about his paper, "Recall and the Serial Position Effect: The Role of Primacy and Recency on Accounting Students' Performance." Jackie Daniel, AUC Woodruff Library, is the interviewer
Generation of osteoinductive grafts by three-dimensional perfusion culture of human bone marrow cells into porous ceramic scaffolds
No full textThe main aims of this thesis were (i) to identify and develop a system that could be
reproducibly used to streamline manufacture of osteoinductive grafts based on human bone marrow
stromal cells (BMSC) in the context of regenerative medicine, (ii) to characterize the developed
system in order to identify key elements responsible for its reproducible and efficient performance,
and (iii) to extend its use to a sheep cell source, thus opening the way to test the osteoinductivity of
orthotopic implants in a large animal model.
Bone Marrow Stromal Cells (BMSC), which are typically defined by their capacity to adhere
on plastic [1] and form a fibroblastic colony (CFU-f) [2], represent a very low fraction (approximately
0.01%) among the nucleated cells of the bone marrow. Therefore, to obtain a sufficient number of
cells for bone tissue engineering applications, BMSC are typically first selected and expanded in
monolayer (2D) prior to loading into 3D scaffolds. However, 2D-expansion causes BMSC to
progressively lose their early progenitor properties and differentiation potential [3-5], and to decrease
their capability to form colonies and to induce bone tissue formation upon ectopic implantation [3],
placing several potential limits on their clinical utility. To bypass the process of 2D-expansion and its
associated limitations, we used an innovative bioreactor-based approach to seed, expand, and
differentiate BMSC directly in a 3D ceramic scaffold [6]. Nucleated cells, freshly isolated from a bone
marrow aspirate, were introduced into the bioreactor system and perfused through the pores of 3D
ceramics for five days, then further cultured under perfusion for an additional two weeks. Using the
developed procedure, BMSC could be seeded and extensively expanded within the 3D environment of
the ceramic pores. Interestingly, we found that the 3D-generated constructs contained both
hemopoietic cells and BMSC, whose relative fractions could be modulated by appropriate media
supplements, and that a consistent fraction of expanded BMSC was clonogenic. In contrast, following
the typical 2D-expansion, cells of the hemopoietic lineage could not be maintained, and, consistently
with previous studies, only a minor fraction of expanded BMSC was still clonogenic. When constructs
were ectopically implanted in nude mice, those engineered in the bioreactor reproducibly generated
bone tissue that was uniformly distributed throughout the scaffold volume and filled up to 60% of the
ceramic pores. In marked contrast, when similar numbers of 2D-expanded BMSC were loaded into
ceramic scaffolds and implanted, bone was infrequently generated, and even in the most
osteoinductive constructs, it was localized to peripheral regions, filling only 10% of the ceramic pore
volume [6].
Considering the need of reproducibility or at least of predictability in the osteoinductive ability
of the constructs for their standardized clinical use, in order to validate the possibility of extending the
use of the developed bioreactor-based approach for generating osteoinductive grafts of clinically
relevant size, we then investigated whether a minimum cell density was required for the reproducible
bone tissue formation. Based on the established association between the higher clonogenicity of
BMSC expanded in the 3D-system and the more reproducible and extensive osteoinductivity of the
resulting constructs, as compared to those based on 2D-expanded BMSC, we demonstrated that
presence or absence of bone in the constructs following ectopic implantation is related not to the total
number of implanted BMSC, but to the number of CFU-f present in the construct at the time of
implantation. In particular, we identified an apparent threshold in the amount of CFU-f discriminating
between osteoinductive and not osteoinductive constructs.
The developed bioreactor-based approach has been validated in a heterotopic model. Before
envisioning a clinical trial in human, a study in a large animal model is needed to validate the safety
and the surgical feasibility of the overall procedure. Thus, in the perspective of testing our novel
approach for repairing experimental bone defects in a sheep model, it was first necessary to validate
our system using ovine BMSC. We demonstrated that osteoinductive constructs can be generated by
perfusing 3D ceramic scaffolds with the nucleated cell fraction of ovine bone marrow aspirates [7].
Ongoing studies in the context of an EU-funded Project are aimed at testing the capability of the
generated constructs to repair large bone defects in sheep (i.e. defects around titanium implants
inserted into trabecular bone of the proximal humerus, and postero-lateral spinal fusion in lumbarregion)
"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States" By M. Carey.
No full text"Reflections on the subject of Emigration from Europe with a view to Settlement in the United States: containing bried sketches of the moral and political character of those states.
By M. Carey, member of the American philosophical, and of the American Antiquarian Society, and author of The Olive Branch, Cindiciae Hibernicae, essays on banking, on political economy, and on internal improvement.
To which are now added the English editor's comments on the subject; together with Important Advice to Emigrants, and Cautions Against Impositions Practiced in the Outports
Dispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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