Altered Affinity Maturation in Primary Response to (4-hydroxy-3-nitrophenyl) Acetyl (NP) after Autologous Reconstitution of Irradiated C57BL/6 Mice

Immune responses developing in irradiated environment are profoundly altered. The memory anti-arsonate response of A/J mice is dominated by a major clonotype encoded by a single gene segment combination called CRIA. In irradiated and autoreconstituted A/J mice, the level of anti-ARS antibodies upon secondary immunization is normal but devoid of CRIA antibodies. The affinity maturation process and the somatic mutation frequency are reduced. Isotype switching and development of germinal centers (GC) are delayed

The analytical application of the galvanic dissolution of niobium and tantalum : the determination of nitrogen

Nitrogen is a contaminant of niobium and tantalum adversely affecting the workability of the metal. With recent interest in the refractory metals, one problem the chemical analyst must solve is the accurate determination of nitrogen in niobium and tantalum at very low levels. The usual method of assaying for nitrogen in metals uses a modification of the Kjeldahl fixation with subsequent distillation of the ammonia. The dissolution of niobium and tantalum was studied to elucidate a method in which a quantitative recovery of nitrogen could be attained in an economical period of time. Galvanic coupling of the sample with a more noble metal was found to increase the dissolution rates several fold. Methods using rhodium and osmium salts with tantalum and rhodium and platinum salts with niobium were developed using in situ coupling for more efficient contact. The proposed methods were checked against "standard" procedures, and against a recent method using iodate and hydrofluoric acid to promote dissolution

CD4+ CD25+ Regulatory T Cells Control T Helper Cell Type 1 Responses to Foreign Antigens Induced by Mature Dendritic Cells In Vivo

Recent evidence suggests that in addition to their well known stimulatory properties, dendritic cells (DCs) may play a major role in peripheral tolerance. It is still unclear whether a distinct subtype or activation status of DC exists that promotes the differentiation of suppressor rather than effector T cells from naive precursors. In this work, we tested whether the naturally occurring CD4+ CD25+ regulatory T cells (Treg) may control immune responses induced by DCs in vivo. We characterized the immune response induced by adoptive transfer of antigen-pulsed mature DCs into mice depleted or not of CD25+ cells. We found that the development of major histocompatibility complex class I and II–restricted interferon γ–producing cells was consistently enhanced in the absence of Treg. By contrast, T helper cell (Th)2 priming was down-regulated in the same conditions. This regulation was independent of interleukin 10 production by DCs. Of note, splenic DCs incubated in vitro with Toll-like receptor ligands (lipopolysaccharide or CpG) activated immune responses that remained sensitive to Treg function. Our data further show that mature DCs induced higher cytotoxic activity in CD25-depleted recipients as compared with untreated hosts. We conclude that Treg naturally exert a negative feedback mechanism on Th1-type responses induced by mature DCs in vivo

Robust Models for Optic Flow Coding in Natural Scenes Inspired by Insect Biology

The extraction of accurate self-motion information from the visual world is a difficult problem that has been solved very efficiently by biological organisms utilizing non-linear processing. Previous bio-inspired models for motion detection based on a correlation mechanism have been dogged by issues that arise from their sensitivity to undesired properties of the image, such as contrast, which vary widely between images. Here we present a model with multiple levels of non-linear dynamic adaptive components based directly on the known or suspected responses of neurons within the visual motion pathway of the fly brain. By testing the model under realistic high-dynamic range conditions we show that the addition of these elements makes the motion detection model robust across a large variety of images, velocities and accelerations. Furthermore the performance of the entire system is more than the incremental improvements offered by the individual components, indicating beneficial non-linear interactions between processing stages. The algorithms underlying the model can be implemented in either digital or analog hardware, including neuromorphic analog VLSI, but defy an analytical solution due to their dynamic non-linear operation. The successful application of this algorithm has applications in the development of miniature autonomous systems in defense and civilian roles, including robotics, miniature unmanned aerial vehicles and collision avoidance sensors

Phenotypic character of phage protein abnormalities induced by bromouracil

The incorporation of bromouracil, a thymine analogue, into the DNA of bacteriophage T2 stimulates the synthesis of significant quantities of abnormal proteins. Their abnormal character is deduced from the study of certain properties of phages produced in the presence of bromouracil: stability of structure, adsorption on a sensitive bacterial strain and immunologic specificity. The modifications studied are not transmitted to the progeny synthesized in the absence of the base analogue. In the presence of bromouracil, the synthesis of phage DNA and protein is much less affected than the synthesis of virus particles. This difference is attributed to the fact that the abnormal proteins cannot be integrated into the phage particles. © 1965.SCOPUS: ar.jinfo:eu-repo/semantics/publishe

Effet du bromouracile sur la synthèse et la structure des protéines de phages

Doctorat en Sciencesinfo:eu-repo/semantics/nonPublishe