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Biomedical subjects

H Wagner

Publications and source records attributed to H Wagner.

At least 1,099 records · Page 61Linked to original sources
PubMedDate not supplied

High speed electrophoresis simulation for optimization of continuous flow electrophoresis and high performance capillary techniques: Part I. Computer model.

A computer program for high-speed simulation and optimization of electrophoretic processes has been developed for carrier-free systems of all kinds. The calculations are based on the one-dimensional dynamic (transient-state) model. The three-dimensional geometry of the simulation space can be chosen deliberately. With a highly efficient transport algorithm instead of complicated integration schemes for the transport equations, the calculation time can be effectively spent on various important parameters such as ionic strength, temperature, Joule heat, activity coefficients and concentration changes due to membranes. The parameter set of any carrier free electrophoretic method (i.e., continuous-flow electrophoresis, capillary isotachophoresis and high performance capillary zone electrophoresis) can be imported directly into the computer program by means of a graphic user interface. The program performs overnight-simulation of any electrophoretic system containing up to 15 components.

Computer Simulation↗
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Influence of the electrode compartment separating membranes on continuous flow electrophoresis.

The influence of the ion permeable diaphragms, separating the electrode compartments of continuous flow electrophoresis chambers from the separation space, are described in detail. A set of equations is derived from a simplified phenomenological model of the ion transport across media boundaries. These equations are useful to predict the magnitude of concentration changes near the membranes due to the electrophoretic ion transport. Adaption to any CFE geometry, membrane material and electrolyte system is possible with only a few measurements, which yield the transference number difference as a characteristic transport property of the membrane material for a special electrolyte. The validity of the equations is checked by experiments. Local electric field strength and local conductivity are measured with a potential gradient-conductivity scanner developed in our laboratory. This device yields data on the dynamics of the concentration changes.

Electrodes↗
PubMedDate not supplied

Effects of (Na+ + K+)-ATPase-specific antibodies of enzymatic activity and monovalent cation transport.

Antibodies have been obtained that specifically interact with the transport enzyme (Na+ + K+)-activated ATPase. The antigen used was purified (Na+ + Ka+)-ATPase from canine renal medulla. Purified gamma globulin from immunized animals, but not from control animals or preimmune serum, inhibited (Na+ + Ka+)-ATPase from canine renal medullar with reduction of activity to 33 +/- 4 (SD)% in concentration-dependent manner. Maximum inhibition occurred in less than 5 minutes at 37 degrees C. The Mg++ -dependent, nonouabain inhibited component of activity (Mg++ -ATPase) was unaffected. Fab fragments obtained by papain cleavage of the gamma globulin fraction had similar inhibitory activity and specificity. These antibodies also produced varying degrees of concentration-related inhibition of canine myocardial, calf brain, and human red cell ghost (Na++ + Ka+)-ATPase, but not Mg++-ATPase activity.

Adenosine Triphosphatases↗
PubMedDate not supplied

Encoding of both vertical and horizontal disparity in random-dot stereograms by Wulst neurons of awake barn owls.

In binocular vision, the lateral displacement of the eyes gives rise to both horizontal and vertical disparities between the images projected onto the left and right retinae. While it is well known that horizontal disparity is exploited by the binocular visual system of birds and mammals to enable depth perception, the role of vertical disparity is still largely unclear. In this study, neuronal activity in the visual forebrain (visual Wulst) of behaving barn owls to vertical disparity was investigated. Single-unit responses to global random-dot stereograms (RDS) were recorded with chronically implanted electrodes and transmitted via radiotelemetry. Nearly half of the cells investigated (44%, 16/36) varied the discharge as a function of vertical disparity. Like horizontal-disparity tuning profiles, vertical-disparity tuning curves typically exhibited periodic modulation with side peaks flanking a prominent main peak, and thus, could be fitted well with a Gabor function. This indicates that tuning to vertical disparity was not caused by disrupting horizontal-disparity tuning via vertical stimulus offset, but by classical disparity detectors whose orientation tuning was tilted. When tested with horizontal in addition to vertical disparity, almost all cells investigated (92%, 12/13) were tuned to both kinds of disparity. The emergence of disparity detectors sensitive in two dimensions (horizontal and vertical) is discussed within the framework of the disparity energy model.

Animals↗
PubMedDate not supplied

Rearing in different photic and chromatic environments modifies spectral responses of cone horizontal cells in adult fish retina.

We investigated chromatic processing in the outer retina of the cichlid fish Aequidens pulcher. Intracellular recordings from cone-specific horizontal cells (CHCs) revealed that the two morphologically identified types (H1 and H2) also have different spectral responses. H1-L cells hyperpolarize to all wavelengths ("luminosity"). H2-Cb cells depolarize to long wavelengths and hyperpolarize to short wavelengths ("chromaticity", biphasic). Furthermore, we verified by immunocytochemistry that H2-Cb cells of A. pulcher predominantly contact the middle-wavelength-sensitive (MWS) members of double cones. Developmental plasticity in the cone-CHC networks was induced by rearing fish under conditions of spectral deprivation and different levels of white light. H1-L spectral responses were unaffected by the rearing conditions. Different intensity levels of white light and deprivation of long wavelengths during rearing both induced changes in the spectral responses of H2-Cb. Deprivation of short and middle wavelengths had no effect. Our results indicate that spectral processing in the outer retina of fishes can be modulated in response to different visual experiences and suggest that developmental fine tuning of the color-vision system occurs at early levels of visual processing.

Adaptation, Physiological↗
PubMedDate not supplied

Biological activity of novel macrocyclic alkaloids (budmunchiamines) from Albizia amara detected on the basis of interaction with DNA.

Extracts derived from Albizia amara were found to demonstrate activity in a recently developed hplc system designed to detect compounds capable of interacting with DNA. Further investigation led to the procurement of four sets of alkaloid isolates X1-X4 that were found to be macrocyclic pithecolobine alkaloids. All four isolates interacted with calf thymus DNA and were generally cytotoxic with a battery of cultured mammalian cells. As determined with Salmonella typhimurium strain TM677, isolates X1 and X3 were bactericidal, but not mutagenic. Isolate X1 was found to inhibit the catalytic activity of DNA polymerase, RNA polymerase, and HIV-1 reverse transcriptase. With DNA polymerase, the reaction was shown to be inhibited in a manner that was competitive with respect to DNA. In addition, isolate X1 inhibited each of the following: platelet aggregation, human lymphocyte transformation, phorbol-ester-induced chemiluminescence with human granulocytes, and cyclooxygenase activity. Detection of these alkaloids on the basis of their interaction with DNA exemplifies the validity of this approach.

Alkaloids↗