Continuous growth of proximal tubular kidney epithelial cells in hormone-supplemented serum-free medium.

An epithelial cell line from pig kidney (LLC-PK1) with properties of proximal tubular cells can be maintained indefinitely in hormone-supplemented serum-free medium. Continuous growth requires the presence of seven factors: transferrin, insulin, selenium, hydrocortisone, triiodothyronine, vasopressin, and cholesterol. The hormone-defined medium (a) supports growth of LLC-PK1 cells at a rate of approaching that observed in serum-supplemented medium; (b) allows vectorial transepithelial salt and fluid transport as measured by hemicyst formation; and (c) influences cell morphology. The vasopressin dependency for growth and morphology can be partially replaced by isobutylmethylxanthine or dibutyryl cyclic AMP. The medium has been used to isolate rabbit proximal tubular kidney epithelial cells free of fibroblasts

Retention of differentiated properties in an established dog kidney epithelial cell line (MDCK).

Madin-Darby canine kidney (MDCK) cells grown in tissue culture have the morphological properties of distal tubular epithelial cells, form tight junctions, and lack several proximal tubular enzyme markers. Adenylate cyclase in these cells was stimulated by vasopressin, oxytocin, prostaglandins E1 and E2, glucagon, and cholera toxin. Hormone-stimulated adenylate cyclase activity in isolated membrane preparations was dependent on low concentrations of GTP and had the MgCl2 and pH optima expected for the kidney enzyme. The results, as well as the demonstration of enhanced hemicyst formation induced by cyclic AMP, suggest that the MDCK cell line has retained the differentiated properties of the kidney epithelial cell of origin. When MDCK cells were injected into baby nude mice, continuous nodule growth was observed until adulthood was attained. Histological studies revealed the presence of two cell types: normal mouse fibroblasts which comprise 80--90% of the solid nodule mass, and MDCK cells, which formed epithelial sheets lining internal fluid-filled glands. Electron microscope analysis showed that the mucosal surfaces of the cells were characterized by microvilli which faced the lumen of the glands, that adjacent MDCK cells were joined by tight junctions, and that the serosal surfaces of the epithelial sheets were characterized by smooth plasma membranes which were lined by a continuous basement membrane. These observations lead to the conclusion that the MDCK cells retain regional differentiation of their plasma membranes and the ability to regenerate kidney tubule-like structures in vivo

Stability of Control Systems with Multiple Sector-Bounded Nonlinearities for Inputs Having Bounded Magnitude and Bounded Slope

This paper considers the input-output stability of a control system that is composed of a linear time-invariant multivariable system interconnecting with multiple decoupled time-invariant memoryless nonlinearities. The objectives of the paper are twofold. First and foremost, we prove (under certain assumptions) that if the multivariable Popov criterion is satisfied, then the system outputs and the nonlinearity inputs are bounded for any exogeneous input having bounded magnitude and bounded slope, and for all the nonlinearities lying in given sector bounds. As a consequence of using the convolution algebra, the obtained result is valid for rational and nonrational transfer functions. Second, for the case in which the transfer functions associated with the Popov criterion are rational functions, we develop a useful inequality for stabilizing the system by numerical methods. This is achieved by means of the positive real lemma and known results on linear matrix inequalities. To illustrate the usefulness of the inequality, a numerical example is provided

Prioritizing Land for Conservation in Northeast North Carolina

The northeastern coastal plain of North Carolina provides a number of irreplaceable values like habitat for wildlife, economic gain through tourism, and social value through recreation and aesthetics. New development in this region may alter existing undeveloped lands that are important to wildlife and the community. In order to preserve lands in the face of this threat, land trusts like the North Carolina Coastal Land Trust (NCCLT) work to protect lands from development in perpetuity. Due to limited funds and resources, land trusts must ensure projects they undertake are both within the mission of the organization and of high conservation value. Site prioritization schemes are a way to aid the decision making process when undergoing conservation projects. In coordination with the North Carolina Coastal Land Trust, this study uses a multi-criteria decision analysis and GIS site prioritization to identify parcels of high conservation value in 5 priority regions within North Carolina’s northeastern coastal plain. Parcel level prioritization analyses were performed in ArcGIS using a utility analysis and value-based framework to determine parcels of highest conservation significance. Criteria included in this framework were based on acreage, connectivity with other managed lands, biodiversity, threat of development, and riparian frontage. As part of this process, a GIS Land Prioritization tool was developed that (1) provides summary statistics of important conservation criteria for each parcel across any region of land; (2) allows for manipulation of the actual prioritization method, weighting of values, and point scheme so the land trust can prioritize certain criteria differently in future analyses; and (3) outputs a list of parcels and their associated conservation scores for each parcel depending on the point scheme and weights defined by the user. While the tool allows for any number of point schemes to be used, the analysis performed here uses an equal weighting method across criteria. Results indicate a range of conservation values for parcels in each priority region. The findings from this study and the GIS tool created can be used both proactively and reactively in conservation planning efforts and project decision making in North Carolina

Design of Control Systems with Multiple Backlash Nonlinearities Subject to Inputs Restricted in Magnitude and Slope

This paper develops a computational method for designing a control system that is an interconnection of transfer functions and multiple decoupled backlash nonlinearities where each backlash is modelled as an uncertain band containing multi-valued functions. The design objective is to ensure that the system outputs and the nonlinearity inputs always stay within their prescribed bounds in the presence of all inputs whose magnitude and whose slope are bounded by respective numbers. By using a known technique, each backlash is decomposed as a linear gain and a bounded disturbance. Essentially, the original design problem is replaced by a surrogate design problem that is related to a linear system and thereby can readily be solved by tools available in previous work. Moreover, as a result of using the convolution algebra A, the method developed here is applicable to rational and nonrational transfer functions. To illustrate the usefulness of the method, linear decentralized controllers are designed for a binary distillation column where valve stiction characteristics are taken into account

Korea under Japanese colonial administration

Thesis (M.A.)--Boston UniversityThe present paper is an analytical study in which an attempt is made to evaluate the Japanese administration on Korea through a comparison with the concept and philosophy of democratic administrative institutions which prevail in the United States and an assessment of the extent to which the Japanese administrative system did meet the needs of the Korean people, thereby determining what elements of the two administrative systems may prove most valuable in the future development of Korean public administration. One assumption must be made for the purpose, namely, that democratic institutions are best adapted to the needs of the Korean people at this time