University of Cologne

About: University of Cologne is a education organization based out in Cologne, Germany. It is known for research contribution in the topics: Population & Transplantation. The organization has 32050 authors who have published 66350 publications receiving 2210092 citations. The organization is also known as: Universität zu Köln & Universitatis Coloniensis.

Dynamic transitions and hysteresis

Abstract: When an interacting many-body system, such as a magnet, is driven in time by an external perturbation, such as a magnetic field, the system cannot respond instantaneously due to relaxational delay. The response of such a system under a time-dependent field leads to many novel physical phenomena with intriguing physics and important technological applications. For oscillating fields, one obtains hysteresis that would not occur under quasistatic conditions in the presence of thermal fluctuations. Under some extreme conditions of the driving field, one can also obtain a nonzero average value of the variable undergoing such ``dynamic hysteresis.'' This nonzero value indicates a breaking of the symmetry of the hysteresis loop about the origin. Such a transition to the ``spontaneously broken symmetric phase'' occurs dynamically when the driving frequency of the field increases beyond its threshold value, which depends on the field amplitude and the temperature. Similar dynamic transitions also occur for pulsed and stochastically varying fields. We present an overview of the ongoing research in this not-so-old field of dynamic hysteresis and transitions.

Multifunctionality of plant ABC transporters – more than just detoxifiers

Abstract: The ABC-transporter superfamily is one of the largest protein families, and members can be found in bacteria, fungi, plants and animals. The first reports on plant ABC transporters showed that they are implicated in detoxification processes. The recent completion of the genomic sequencing of Arabidopsis thaliana (L.) Heynh. [Arabidopsis Genome Initiative (2000) Nature 408:796-815] showed that Arabidopsis contains more than 100 ABC-type proteins; 53 genes code for so-called full-size transporters, which are large proteins of about 150 kDa consisting of two hydrophobic and two hydrophilic domains. The large number of genes in the MDR/MRP and PDR5-like sub-clusters and the strong sequence homology found in many cases suggest functional redundancy. One reason for the high number of genes can be attributed to the duplication of large segments of Arabidopsis chromosomes. Recent results indicate that the function of this protein family is not restricted to detoxification processes. Plant ABC transporters have been demonstrated to participate in chlorophyll biosynthesis, formation of Fe/S clusters, stomatal movement, and probably ion fluxes; hence they may play a central role in plant growth and developmental processes.

Sequence homologies, N sequence insertion and JH gene utilization in VHDJH joining: implications for the joining mechanism and the ontogenetic timing of Ly1 B cell and B-CLL progenitor generation.

Abstract: Sequence analysis of rearranged VHDJH genes of B lineage cells from various stages of ontogeny indicates that short sequence homologies at the breakpoints of recombination contribute to V region gene assembly. Such homologies are regularly seen at DJH junctions of neonatal pre-B cells, most of which do not contain N sequences. In the same cells, but not at later developmental stages, preferential usage of the JH1 element is observed. After birth, N sequence insertion increases with time and is always more prominent at the VHD border than the DJH border. In pre-B cells from adult animals and in mature B cells, in cases where N sequences were not detectable, sequence homologies at the DJH border were found in only half of the instances. This lower incidence could be due to N sequence addition to one of the recombining DNA ends and/or cellular selection. Inspection of VHDJH junctions for N sequence insertion, sequence homologies at the DJH border and JH1 usage allows the estimation of the timepoint in ontogeny at which particular B cell subsets are seeded into the immune system. Specifically, the present data show that the cells of the Ly1 B cell subset are generated not only neonatally but also beyond the first weeks of life. However, the DJH junctions of the progenitors of chronic B cell leukemias which originate from the same B cell subset resemble those of neonatal pre-B cells, suggesting that these cells have already undergone a transforming event at this early developmental stage.

HIV-1 antibody 3BNC117 suppresses viral rebound in humans during treatment interruption

Abstract: Interruption of combination antiretroviral therapy in HIV-1-infected individuals leads to rapid viral rebound. Here we report the results of a phase IIa open label clinical trial evaluating 3BNC117,a broad and potent neutralizing antibody against the CD4 binding site of the HIV-1 Env protein, during analytical treatment interruption in 13 HIV-1-infected individuals. Participants with 3BNC117-sensitive virus outgrowth cultures were enrolled. Results show that two or four 30 mg kg(-1) 3BNC117 infusions,separated by 3 or 2 weeks, respectively, are generally well tolerated.Infusions are associated with a delay in viral rebound of 5-9 weeks after two infusions, and up to 19 weeks after four infusions, or an average of 6.7 and 9.9 weeks, respectively, compared with 2.6 weeks for historical controls (P < 0.00001). Rebound viruses arise predominantly from a single provirus. In most individuals,emerging viruses show increased resistance, indicating escape.However, 30% of participants remained suppressed until antibody concentrations waned below 20 μg ml(-1), and the viruses emerging in all but one of these individuals showed no apparent resistance to 3BCN117, suggesting failure to escape over a period of 9-19 weeks.We conclude that the administration of 3BNC117 exerts strong selective pressure on HIV-1 emerging from latent reservoirs during analytical treatment interruption in humans.