Biomedical subjects

W Hage

Publications and source records attributed to W Hage.

5 recordsLinked to original sources

PubMed2001

Automated topographical cell proliferation analysis.

BACKGROUND: Cell proliferation is often studied using the incorporation of bromodeoxyuridine (BrdU). Immunohistochemical staining is then used to detect BrdU in the nucleus. To circumvent the observer bias and labor-intensive nature of manually counting BrdU-labeled nuclei, an automated topographical cell proliferation analysis method is developed. METHODS: Sections stained with fluorescein-labeled anti-BrdU and counterstained with To-Pro-3 are scanned using confocal laser scanning microscopy (CLSM). For every point in the image, the nucleus density of BrdU-labeled nuclei and the total nucleus density of the neighborhood of that point are calculated from the BrdU and the To-Pro-3 signal, respectively. The ratio of these densities gives an indication of the amount of cell proliferation at that point. The automated measure is validated by comparing it with the ratio of BrdU-stained nuclei to the total number of nuclei obtained from a manual count. RESULTS: A positive correlation is found between the automated measure and the ratios calculated from the manual counting (r = 0.86, P < 0.001). Calculating the topographical cell proliferation using the automated method is faster and does not suffer from interobserver variability. CONCLUSIONS: Automated topographical cell proliferation analysis is a fast method to objectively find differences in cell proliferation within a tissue. This can be visualized by a topographical map that corresponds to the tissue under study.

Animals↗

PubMed2000

Fluid mechanics of biological surfaces and their technological application.

A survey is given on fluid-dynamic effects caused by the structure and properties of biological surfaces. It is demonstrated that the results of investigations aiming at technological applications can also provide insights into biophysical phenomena. Techniques are described both for reducing wall shear stresses and for controlling boundary-layer separation. (a) Wall shear stress reduction was investigated experimentally for various riblet surfaces including a shark skin replica. The latter consists of 800 plastic model scales with compliant anchoring. Hairy surfaces are also considered, and surfaces in which the no-slip condition is modified. Self-cleaning surfaces such as that of lotus leaves represent an interesting option to avoid fluid-dynamic deterioration by the agglomeration of dirt. An example of technological implementation is discussed for riblets in long-range commercial aircraft. (b) Separation control is also an important issue in biology. After a few brief comments on vortex generators, the mechanism of separation control by bird feathers is described in detail. Self-activated movable flaps (= artificial bird feathers) represent a high-lift system enhancing the maximum lift of airfoils by about 20%. This is achieved without perceivable deleterious effects under cruise conditions. Finally, flight experiments on an aircraft with laminar wing and movable flaps are presented.

Animals↗

PubMed1998

Carbonic acid in the gas phase and its astrophysical relevance

In outer space, high-energy irradiation of cryogenic ice mixtures of abundant water and carbon dioxide is expected to form solid carbonic acid. Experiments and thermodynamic analyses show that crystalline carbonic acid sublimates without decomposition. Free-energy considerations based on highly accurate molecular quantum mechanics, in combination with vapor pressures resulting from experimental sublimation rates, suggest that in the gas phase, a monomer and dimer of carbonic acid are in equilibrium, comparable to that of formic acid. Gaseous carbonic acid could be present in comets, on Mars and outer solar system bodies, in interstellar icy grains, and in Earth's upper atmosphere.

Journal Article↗

PubMed1997

Association and colocalization of Eps15 with adaptor protein-2 and clathrin.

Eps15 has been identified as a substrate of the EGF receptor tyrosine kinase. In this report, we show that activation of the EGF receptor by either EGF or TGF-alpha results in phosphorylation of Eps15. Stimulation of cells with PDGF or insulin did not lead to Eps15 phosphorylation, suggesting that phosphorylation of Eps15 is a receptor-specific process. We demonstrate that Eps15 is constitutively associated with both alpha-adaptin and clathrin. Upon EGF stimulation, Eps15 and alpha-adaptin are recruited to the EGF receptor. Using a truncated EGF receptor mutant, we demonstrate that the regulatory domain of the cytoplasmic tail of the EGF receptor is essential for the binding of Eps15. Fractionation studies reveal that Eps15 is present in cell fractions enriched for plasma membrane and endosomal membranes. Immunofluorescence studies show that Eps15 colocalizes with adaptor protein-2 (AP-2) and partially with clathrin. No colocalization of Eps15 was observed with the early endosomal markers rab4 and rab5. These observations indicate that Eps15 is present in coated pits and coated vesicles of the clathrin-mediated endocytic pathway, but not in early endosomes. Neither AP-2 nor clathrin are required for the binding of Eps15 to coated pits or coated vesicles, since in membranes lacking AP-2 and clathrin, Eps15 still shows the same staining pattern. These findings suggest that Eps15 may play a critical role in the recruitment of active EGF receptors into coated pit regions before endocytosis of ligand-occupied EGF receptors.

3T3 Cells↗

PubMed1995

Cell fate in the Arabidopsis root meristem determined by directional signalling.

Postembryonic development in plants is achieved by apical meristems. Surgical studies and clonal analysis have revealed indirectly that cells in shoot meristems have no predictable destiny and that position is likely to play a role in the acquisition of cell identity. In contrast to animal systems, there has been no direct evidence for inductive signalling in plants until now. Here we present evidence for such signalling using laser ablation of cells in the root meristem of Arabidopsis thaliana. Although these cells show rigid clonal relationships, we now demonstrate that it is positional control that is most important in the determination of cell fate. Positional signals can be perpetuated from more mature to initial cells to guide the pattern of meristem cell differentiation. This offers an alternative to the general opinion that meristems are the source of patterning information.

Arabidopsis↗