Some new findings about Hofbauer cells in the chorionic villi of the human placenta

The cytological structure of the Hofbauer cells was investigated in human placentas of the first and second trimesters of gestation. These cells are found in the stromal channel system of the chorionic villi core. Their walls, which are supported by collagen fiber bundles, are produced by reticulum cells and fibroblasts. The cytoplasmic processes of the Hofbauer cells are in contact with the walls of the channels without being associated with them by desmosomal complexes. Some of these cells have features in common with macrophages, such as cytoplasmic processes, larger vacuoles, many pinocytotic vesicles and intracytoplasmic granules. This system of vacuoles and vesicles enables micropinocytotic activity and phagocytosis. This type of Hofbauer cell resembles the typical macrophages. These cells may play a role in the regulation of stromal water content, transportation of ions and the flow of interstitial fluid. The most original finding of this study are long tubes observed in some Hofbauer cells and extending between the nucleus and the extracellular ground substance through the cytoplasm. One of these tubular formations resembles a cilium in structure with three limiting membranes and is filled with a slightly electron-dense substance. This type of Hofbauer cell may transport information between the nucleus and the extracellular ground substance by means of these tubular structures.     

Probiotics and health: new facts and ideas

Many trials on probiotics are now published that use established methods to demonstrate their clinical efficacy. Convincing progress has been made in the field of inflammatory bowel disease and allergy prevention in infants. Experimental studies show clear differences (and even sometimes opposite effects) between apparently closely related probiotics and suggest new mechanisms for the observed effects, such as immunostimulation by bacterial DNA and interaction with Toll-like receptors and dendritic cells in the gastrointestinal tract.     

Geophysiological modeling: new ideas on modeling the evolution of ecosystems.

Living organisms evolve within ecological associations (from ecosystems to the biosphere) that are constituted by a biological component and a physico-chemical component. It is generally supposed that interactions such as competition and predation between the biological components of ecosystems are the main cause for the observed organization of ecosystems. We believe that in the search for a more comprehensive theory of evolution a much greater attention should be paid to the ways in which living organisms interact with the physico-chemical environment. To test our ideas, we develop a mathematical model to study the evolution of ecosystems, and we apply it to the study of hydrothermal vents. The model proposed is still a qualitative model. It tries to study, in a first approximation, the behaviours of the biological and chemical components. In the following we hope to develop and to improve it so to give a more realistic model.     

The review of contemporary ideas about the influence of flow rate on blood clotting

Normal blood clotting is vitally important for mammals. The diffusion-convection transfer of clotting factors plays a key role in blood clot formation. Since the shear rates of blood flow are very high (up to 7000 s⁻¹), clot formation critically depends on the flow rate. The methods of study of the flow effect on clotting are indirect and the processes are rather complex; therefore, mathematical models of this process are significant for interpretation of results and understanding of the mechanisms. The review expounds the main experimental data on the effect of flow on the blood clotting cascade, some hypotheses and mathematical models explaining different regimes of the functioning of this system. The review is focused on specific problems encountered by researchers in this field. Some of the experimental works have shown that flow decreases the size of the formed fibrin clot and that the dependence of clot formation period on the flow shear rate is a threshold function. However, there are also experimental evidence that the flow can increase production of clotting factors (factor Xa), which must be expressed in the procoagulant action of the flow. Mathematical models of different aspects of clotting give no unified predictions either. Nevertheless, the combined analysis of results of detailed modeling and experiments, in our opinion, may result in understanding of the mechanisms, which determine the behavior of clotting in a flow.     

The promise of new ideas and new technology for improving teaching and learning

There have been enormous advances in our understanding of human learning in the past three decades. There have also been important advances in our understanding of the nature of knowledge and new knowledge creation. These advances, when combined with the explosive development of the Internet and other technologies, permit advances in educational practices at least as important as the invention of the printing press in 1460. We have built on the cognitive learning theory of David Ausubel and various sources of new ideas on epistemology. Our research program has focused on understanding meaningful learning and on developing better methods to achieve such learning and to assess progress in meaningful learning. The concept map tool developed in our program has proved to be highly effective both in promoting meaningful learning and in assessing learning outcomes. Concept mapping strategies are also proving powerful for eliciting, capturing, and archiving knowledge of experts and organizations. New technology for creating concept maps developed at the University of West Florida permits easier and better concept map construction, thus facilitating learning, knowledge capture, and local or distance creation and sharing of structured knowledge, especially when utilized with the Internet. A huge gap exists between what we now know to improve learning and use of knowledge and the practices currently in place in most schools and corporations. There are promising projects in progress that may help to achieve accelerated advances. These include projects in schools at all educational levels, including projects in Colombia, Costa Rica, Italy, Spain, and the United States, and collaborative projects with corporate organizations and distance learning projects. Results to date have been encouraging and suggest that we may be moving from the lag phase of educational innovation to a phase of exponential growth.     

A new location-scale test based on a combination of the ideas of Levene and Lepage

Lepage's test combines the Wilcoxon rank-sum and the Ansari-Bradley statistics. We propose to replace the latter statistic by a Wilcoxon rank-sum calculated after Levene's transformation. We use the medians for this transformation, i.e. absolute deviations from sample medians are calculated. The new location-scale test can be carried out as a permutation test based on permutations of the original observations, the Levene transformation has to be applied for each permutation in an intermediate step to calculate the test statistic. Simulations indicate that the new test can be more powerful than an O'Brien-type test and Lepage's test, the latter is the standard nonparametric location-scale test. The new test is illustrated using real data about colony sizes of yellow-eyed penguins and an SAS program to perform the test is freely available.     

Protein folding mechanisms: new methods and emerging ideas

During the past year, advances in our understanding of folding mechanisms have been made through detailed experimental and theoretical studies of a number of proteins. The development of new methods has allowed the earliest events in folding to be probed and the measurement of folding at the level of individual molecules is now possible, opening the door to exciting new experiments.