Adhesion and spreading of cultured endothelial cells on modified and unmodified poly(ethylene terephthalate): a morphological study

The in vitro adhesion and spreading of human endothelial cells (HEC) on hydrophobic poly(ethylene terephthalate) (PETP) and moderately wettable tissue culture polyethylene terephthalate) (TCPETP) were studied with light microscopy and electron microscopy. Numbers of HEC adhering on TCPETP were always higher than those found on PETP. When cells were seeded in the presence of serum, extensive cell spreading on both PETP and TCPETP was observed after the first 30 min. Thereafter, spread cells appeared to withdraw from the PETP surface, resulting in irregularly shaped cells. Complete cell spreading occurred on TCPETP. Complete cell spreading also occurred on PETP and TCPETP when HEC had first been seeded from phosphate buffer solution and serum was supplied after 30 min. Furthermore, HEC spread on both PETP and TCPETP when the surfaces were precoated with protein(s), which promotes cell adhesion. However, when plasma was used for the coating, spread cells did not proliferate in a monolayer pattern. This study shows that TCPETP is, in general, a better surface for adhesion and proliferation of HEC than is PETP, suggesting that vascular prostheses with a TCPETP-like surface will perform better in vivo than prostheses made of PETP

Human activin-A is expressed in the atherosclerotic lesion and promotes the contractile phenotype of smooth muscle cells

Activin is a member of the transforming growth factor-beta superfamily, and it modulates the proliferation and differentiation of various target cells. In this study, we investigated the role of activin in the initiation and progression of human atherosclerosis. The expression of activin, its physiological inhibitor follistatin, and activin receptors were assayed in human vascular tissue specimens that repr

Natural and anthropogenic forcing of Holocene lake ecosystem development at Lake Uddelermeer (The Netherlands)

The majority of water bodies in the world is affected by human impact on their catchment, and pollution of freshwater ecosystems is now considered a global problem. Palaeoecological research allows to reconstruct the natural ecosystem variability of such polluted systems, and many reconstructions that date back a few centuries or beyond inform on the natural background of polluted lakes. Only a limited number of studies have so far looked at long term (e.g. Holocene) changes in lake ecosystem status, even though human impact is known to date back for several millennia in some parts of the world. We apply a combination of classic palaeoecological proxies and novel geochemical proxies in our study of the Holocene sediments of Lake Uddelermeer (The Netherlands). Lake Uddelermeer is a shallow freshwater lake that is currently characterized by turbid conditions. These are currently thought to have resulted from increased agricultural activity in the 20th century AD, but human impact in the surroundings of this site date back to 6000 BP (late Mesolithic/ early Neolithic). We show that the lake ecosystem was characterized by a mix of aquatic macrophytes and abundant phytoplankton throughout the Early and Middle Holocene (11.5-6 cal kyr BP). A transition to a lake ecosystem with clear-water conditions and relatively high abundances of ‘isoetids’ coincides with the first signs of human impact on the landscape around Lake Uddelermeer (6000 cal yr BP). An abrupt and dramatic ecosystem shift can be seen at ~1030 cal yr BP when increases in the abundance of algal microfossils and concentrations of sedimentary pigments indicate a transition to a turbid phytoplankton-dominated state. A strong increase in concentrations of faecal biomarkers can be seen only after 1950 AD, indicating that an increased input of manure-derived material into the lake is not the initial cause for eutrophication of the system. Canonical Correspondence Analysis (CCA) suggests that reconstructed lake ecosytem changes are best explained by environmental drivers that show long-term gradual changes (sediment age, water depth). These combined results document the long-term anthropogenic impact on the ecosystem of Lake Uddelermeer and provide evidence for pre-Industrial Era signs of eutrophication

ON COMPUTER SIMULATION AS A COMPONENT IN INFORMATION SYSTEMS RESEARCH

Computer simulation is widely regarded as a useful activity during various phases of research. However, depending on its context, the meaning, definition, and focus of the term can vary: In traffic planning, for example, simulation is used to determine useful configurations of a road network, thus focusing on the environment. An entirely different perspective is used within multi-agent systems. In such settings, the environment of the agents remains static, while the interesting research questions concern the behavior of the agents themselves. The research focuses on the microscopic level and the resulting emergent behavior. This article puts such diverse meanings in the context of a research process that treats descriptive and prescriptive research as two sides of the same coin. We develop a framework to classify different types of simulation, based on the actual research activity they are intended to be used for. Two case studies supplement the framework

Replication is more than hitting the lottery twice

The main goal of our target article was to provide concrete recommendations for improving the replicability of research findings. Most of the comments focus on this point. In addition, a few comments were concerned with the distinction between replicability and generalizability and the role of theory in replication. We address all comments within the conceptual structure of the target article, and hope to convince readers that replication in psychological science amounts to much more than hitting the lottery twice

Induction of tyrosine aminotransferase by dibutyryl cyclic-AMP in synchronized hepatoma cells

In Hepatoma Tissue Culture (HTC) cells induction of tyrosine aminotransferase (TAT) by dibutyryl cAMP (DBcAMP) is regulated at some posttranscriptional step. In synchronized HTC cells TAT can be induced by DBcAMP in late G1 and in the S phase of the cell cycle only

The social relations model in research on family systems

Item does not contain fulltex