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Biomedical subjects

E Scholl

Publications and source records attributed to E Scholl.

At least 19 recordsLinked to original sources
PubMed2000

Karhunen-Loeve local characterization of spatiotemporal chaos in a reaction-diffusion system

By computing the Karhunen-Loeve decomposition (KLD) correlation length xi(KLD) of a reaction-diffusion system in the extensive chaos regime, we show that it is a sensitive measure of spatial dynamical inhomogeneities. It reveals substantial spatial nonuniformity of the dynamics at the boundaries and can also detect slow spatial variations in system parameters. The intensive length xi(KLD) can be easily computed from small local subsystems and is found to have a similar parametric dependence as the two-point correlation length computed over the full system size.

Journal Article↗
PubMed2000

Wave fronts may move upstream in semiconductor superlattices

In weakly coupled, current biased, doped semiconductor superlattices, domain walls may move upstream against the flow of electrons. For appropriate doping values, a domain wall separating two electric-field domains moves downstream below a first critical current, it remains stationary between this value and a second critical current, and then moves upstream above. These conclusions are reached by using a comparison principle to analyze a discrete drift-diffusion model, and validated by numerical simulations. Possible experimental realizations are suggested.

Journal Article↗
PubMed2000

Competing spatial and temporal instabilities in a globally coupled bistable semiconductor system near a codimension-two bifurcation

We study complex spatiotemporal dynamics in a globally coupled bistable reaction-diffusion model on a two-dimensional spatial domain. It is demonstrated that complex behavior appears near a codimension-two bifurcation point due to the competition of spatial and temporal instabilities. We derive sufficient conditions for the appearance of mixed spatiotemporal modes, and clarify the origin of a menagery of complex dynamics, such as periodic and chaotic oscillations of current filaments, low-dimensional spatiotemporal chaos including a Shil'nikov attractor, and periodic back-and-forth motion of current density fronts. Such dynamics is found in a wide range of domain sizes for square and rectangular domains. The type of dynamics is sensitive to small variations in the domain shape. We discuss and explain the differences between spatiotemporal dynamics on one-dimensional and two-dimensional domains.

Journal Article↗
PubMed1996

Comparative investigation of drug delivery of collagen implants saturated in antibiotic solutions and a sponge containing gentamicin.

Collagen implants of various structures and a gelatine sponge were placed in five different antibiotic solutions until complete saturation occurred. The antibiotics were chosen to represent different drug classes (gentamicin sulphate, cefotaxim, fusidic acid, clindamycin, vancomycin). The collagen implants saturated with antibiotic solution and a lyophilized collagen sponge containing gentamicin sulphate were eluated in 0.066 M phosphate buffer (pH = 7.4) at 37 degrees C. The total eluation period is 7 d with buffer changes every 24 h. The antibiotic delivery by the collagen implants and the lyophilized sponge containing gentamicin sulphate is complete after a maximum of 4 d. If an implant that has a protective effect against wound infections over a period of 24-48 h is required, the materials described here are suitable. However, where treatment in infected areas should ensure antibiotic cover for 5-10 d, neither collagen materials immersed in antibiotic solutions nor collagen sponges containing gentamicin are suitable.

Anti-Bacterial Agents↗
PubMed1995

Characterization of mouse CD53: epitope mapping, cellular distribution and induction by T cell receptor engagement during repertoire selection.

The pan-leukocyte antigen CD53 is a member of the poorly understood transmembrane 4 superfamily (TM4SF) of cell membrane glycoproteins. CD53 is proposed to play a role in thymopoiesis, since rat CD53 is expressed on immature CD4-8-thymocytes and the functionally mature single-positive subset, but is largely absent from the intermediate CD4+8+ cells. We have characterized CD53 in the mouse through the production of two new monoclonal antibodies, MRC OX-79 and OX-80, which were raised against the RAW 264 cell line and screened on recombinant CD53 fusion proteins. The epitopes recognized by both antibodies are dependent on disulfide bonding and map to the major extracellular region of CD53, requiring the presence of a single threonine residue at position 154. Mouse CD53 has a molecular mass of 35-45 kDa and is expressed on virtually all peripheral leukocytes, but not on cells outside the lymphoid or myeloid lineages. CD53 expression distinguishes subpopulations of thymocytes in the mouse and resembles the expression pattern of rat CD53. Amongst the immature CD4-8-thymocytes, mouse CD53 is clearly detectable on the earliest CD44high25- subset, but down-regulated on the later CD44high25+, CD44low25+ and CD44low25- stages. Also, the subsequent transient TcR-/low CD4-8+ cells and most CD4+8+ thymocytes express little or no CD53. This is consistent with the idea that cells which are committed to enter the selectable CD4+8+ compartment switch off CD53. The effect of T cell receptor (TcR) engagement on the re-expression of CD53 on CD4+8+ thymocytes was studied both ex vivo and in vitro using F5 mice, transgenic for the H-2b/influenza nucleoprotein-peptide-specific TcR, back-crossed onto an H-2q or H-2b background of RAG-2-deficient mice. CD4+8+ thymocytes from non-selecting H-2q F5 mice are CD53 negative, but in vitro stimulation through the TcR dramatically induces CD53 expression. In contrast, a fraction of CD4+8+ thymocytes from positively selecting H-2b F5 transgenic mice express CD53. Therefore TcR engagement by selecting major histocompatibility complex peptide complexes, or surrogate ligands, induces CD53 expression on otherwise CD53-negative, non-selected CD4+8+ thymocytes. Whether CD53 itself participates as a signaling molecule in further stages of thymic selection is still a matter of speculation.

Amino Acid Sequence↗
PubMed1994

Serological diagnosis of Aujeszky's disease: a comparison between reactions of blood samples from sows and their offspring.

Blood sera from sows and their piglets were compared for their suitability for the serological diagnosis of Aujeszky's disease. Within a few days after parturition, blood and colostrum samples were collected from a total of 104 sows from 8 different gI-vaccinated breeding herds. Three piglets of each litter were bled simultaneously with their mother and again 3 weeks later. All 416 sera reacted positively in the screening for vaccination-induced antibodies. Using the gI ELISA, the sera of 16 sows and their offspring reacted positively, while 86 sows and their piglets reacted negatively and 2 sows and their piglets showed reactions near the test-cutoff. By testing piglets from another 1,300 sows in 37 farms, the practicability of the proposed method was proved. Blood samples were taken at intervals of 4 to 6 weeks from piglets of all sows, which had farrowed in the meantime. Within a six to nine months period, the serological status of a breeding herd could be established.

Animals↗
PubMed1988

[The effect of preventative carazolol treatment on stress reactions in boars during semen collection].

The effect of the beta adrenoceptor blocking agent carazolol on heart and circulatory system, on blood values of the acid-base-equilibrium and on plasma enzymes such as creatine-kinase (CK) and aspartate-amino-transferase (ASAT) was investigated in four clinical healthy boars of the German Landrace and four boars of the Piétrain race before, during and after ejaculation at the phantom. The heart rate during semen collection increased less with treatment than it did without it. The relative diastolic time during exertion was prolonged by carazolol in those boars, which also without pharmacological influence had a very short relative diastolic time. By carazolol injection the systolic blood pressure could be decreased most in those boars, which without treatment had the highest rise of systolic blood pressure during semen collection. Furthermore it was shown, that the highest lactate values, which were found in some boars of the Piétrain race, were reduced most by the influence of carazolol. The blood values of the acid-base-equilibrium were highly negative correlated with the lactate values and changed according to them. The enzyme activities (CK and ASAT) 24 h after semen collection were not influenced by carazolol. Individual differences from boar to boar were evident in all examined parameters and were independent of the effects of carazolol treatment.

Acid-Base Equilibrium↗
PubMed1988

[Stress reaction in boars of the German Landrace and Piétrain breeds during semen collection from the phantom].

The effect of the semen collection procedure at the phantom on heart and circulatory system, on blood values of the acid-base-equilibrium and on plasma enzyme values was investigated in four boars of the German Landrace and four boars of the Piétrain race. In most of the boars tachycardia (heart rate above 239/min), an increase of plasma lactate concentration (above 10.0 mmol/l) and of plasma creatine kinase (CK) concentration (plasma CK above 1,000 U/l) were the consequences of the exertion by semen collection. The extent of the exertional reactions on heart and vasculatory parameters strongly depended on the individual disposition while in most of the metabolic blood values the two different races varied evidently. The values of CK 24 hours after semen collection were related to the plasma lactate concentration as well as to the heart rate during semen collection.

Acid-Base Equilibrium↗
PubMed1976

Effects of myocardial revascularization following acute coronary occlusion in pigs.

In a comparative study in pigs the extent of myocardial infarction has been estimated following a temporary three hour coronary occlusion and following a permanent coronary ligation. For evaluation of the cellular injury the infarct size has been determined by a histochemical staining procedure and correlated with serum enzyme studies (creatine phosphokinase, alpha-hydroxybutyric dehydrogenase) in the surviving animal. No significant difference could be detected between the two experimental groups and the extent of cellular damage was similar. A strict linear correlation was found between the serum enzyme activity plotted logarithmically and the morphological infarct size. Likewise the incidence of ventricular fibrillation depended on the extent of cellular injury. Myocardial revascularization does not appear to benefit a pig heart subjected to an acute coronary occlusion lasting three hours or more. Revascularization may even be harmful by creating a haemorrhagic infarct, as found in all the animals submitted to a transient coronary occlusion.

Animals↗