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G Köhler

Publications and source records attributed to G Köhler.

At least 127 records · Page 7Linked to original sources
PubMed1993

A role for immunoglobulin D: interference with tolerance induction.

We have studied the induction and maintenance of tolerance in the B lymphocyte compartment. Neonatal and adult transgenic mice which expressed either surface IgM (sIgM) or sIgM and sIgD anti-2,4,6-trinitrophenyl (TNP) were treated with soluble mono- and multivalent forms of TNP-modified carriers. We compared the B cell compartment of mice treated with antigen and of littermates injected with phosphate-buffered saline. Antigen-mediated cross-linking of membrane-bound IgM (sIgM) caused deletion of B cells both in neonatal and adult mice with mu and kappa transgenes. Deletion was the result of apoptosis. In mice that carried an additional delta transgene sIgD interfered with tolerance induction. The stage in which the cells were sensitive to deletion was characterized as a transitional stage between immature (sIgMdull, heat-stable antigenbright, B220dull, sIgD-) and more mature (IgMbright, heat-stable antigendull, B220bright, sIgD-) B cells. Surviving cells were functional as measured by receptor-mediated changes in the intracellular free Ca2+ concentration. We propose that when the immature B cells have reached the final stages of maturation IgM always transmits negative signals in the absence of T cell help. When B cells need to be screened against self reactivity IgM is the only antigen receptor expressed. The presence of sIgD protects resting B cells from deletion and allows them to initiate an effective immune response.

Animals↗
PubMed1993

Early B cell development requires mu signaling.

In vitro studies with Abelson murine leukemia virus (AMuLV)-transformed murine pre-B cell lines demonstrated that wild-type mu but not mutant mu chains lacking the first constant domain (mu delta 1) can efficiently induce Ig light (L) chain gene rearrangement. Using antibodies against the cytoplasmic tail of the immunoglobulin co-receptor beta (Ig beta) chain we find mu, but not mu delta 1 chains associated with Ig beta. Since a heterodimer of surface-labeled proteins was co-precipitated with mu we conclude that only wild-type mu is associated with the Ig alpha/Ig beta co-receptor on the surface of pre-B cell lines. Mutant mu delta 1 chains achieve their surface expression by utilizing a glycophospholipid anchor. In vivo analysis of transgenic mice expressing either mu or mu delta 1 transgenes revealed the expected "normal" B cell development in the case of wild-type mu transgenic lymphocytes, but a block in differentiation of mu delta 1 transgenic lymphocytes. The maturation block occurs at the developmental transition of pre-B lymphocytes from the CD43/S7+, CD45R/B220low stage to the CD43/S7-, B220low/high stage in which the majority of L chain gene rearrangements occur. These results, together with the observed inability of the mu delta 1 chains to signal activation of L chain gene joining and to associate Ig alpha/Ig beta in pre-B cell lines suggests that signals mediated by the protein complex composed to mu/Ig alpha/Ig beta are crucial during differentiation of pre-B lymphocytes.

Abelson murine leukemia virus↗
PubMed1993

Constitutive expression of transgenic heat stable antigen (mCD24) in lymphocytes can augment a secondary antibody response.

The murine heat stable antigen (HSA, mouse CD24) is a glycosyl phosphatidylinositol-anchored cell surface protein which is primarily expressed in immature but not mature cells of several hematopoietic lineages and in neuronal tissue. The function of HSA is not known but there is evidence in lymphocytes that it is involved in cell adhesion and in cell activation. We examined the effect of constitutive HSA expression on the maturation and on the function of B and T cells in transgenic mice. Transgenic HSA was strongly expressed throughout all stages of T cell maturation without changes in absolute cell number or proportions of subpopulations both in the thymus and in the periphery. The size of the B cell compartment was also unchanged. Thus, we conclude that in the T lineage the loss of HSA expression is not mandatory for maturation. On the functional level, two parameters of immune function were measured. When the ability to activate peripheral T cells expressing transgenic HSA was tested in a mixed lymphocyte reaction, no significant difference in the stimulation index and cytolytic activity was detected between transgenics and control littermates. However, when immunized with a T cell dependent antigen, transgenic mice showed 10-fold higher serum IgG1 titers. This suggests that the expression of transgenic HSA in cells normally negative for HSA (e.g. peripheral T cells or memory B cells) leads to a better stimulation of lymphocytes during a secondary antibody response.

Animals↗
PubMed1992

A survey of protein-DNA interaction sites within the murine immunoglobulin heavy chain locus reveals a particularly complex pattern around the DQ52 element.

The expression of immunoglobulin (Ig) genes is regulated at two levels: rearrangement of individual gene segments and transcription of continuous genes. To find transacting factors involved in mediating locus- and segment specific gene activation and expression, we surveyed a 3600-bp genomic region of the murine Ig heavy chain locus, spanning from the DQ52 element to the Ig heavy chain intron enhancer. We discovered nine, previously undescribed, protein-DNA complexes and estimated their individual binding-affinity preferences (Kr) by quantitative gel shift measurements. We observed one novel protein DNA interaction at the enhancer, two in the JH1 region and six within a 300-bp region immediately 5' to the DQ52 locus. The latter show a complex and specific binding pattern when comparing nuclear extracts derived from pre-B cells and fibroblasts. Further characterization of the interactions at the DQ52 locus by electron microscopy revealed the preferential formation of a protein complex binding to the DQ52 locus with pre B cell extracts. This behavior and the clustering of interaction sites 5' to the DQ52 element suggest that this region is involved in the regulation of heavy chain gene assembly.

Animals↗
PubMed1992

Pressure distribution and energy flow in the focal region of two different electromagnetic shock wave sources.

In extracorporeal shock wave lithotripsy there is still a lack of knowledge about the basic physical terms that are essential for a scientific comparison of lithotripters with different technologies. The main goal of this article is to introduce the relation between pressure distribution, acoustic energy flow and intensity. The procedure of how these data can be achieved quantitatively is described. Technical data of two different commercially available electromagnetic shock wave sources are presented. The results show that acoustic energy flow and intensity depend on the variation of the shock wave parameters and the focal area.

Electromagnetic Phenomena↗
PubMed1992

What makes a shock wave efficient in lithotripsy?

The aim of this investigation was the connection of quantitative shock wave parameters to stone fragmentation in lithotripsy. We developed an in vitro procedure where eroded craters in artificial stones could be measured with respect to their geometric outlines. By altering the components of an electrodynamic ultrasonic source we obtained a multitude of shock wave foci with physical parameters covering a wide range. With these foci different craters were formed and measured. With a correlation method the quantitative stone erosion could be connected with single physical parameters of the shock waves. As a result we found strict linear dependence of the volume erosion on the effective energy. On the other hand, the peak pressure in the focus revealed to be a poor parameter to qualify the fragmentation efficiency of a lithotripter. Additionally the contribution of the rise time of the shock wave to stone erosion is of negligible influence.

Equipment Design↗
PubMed1992

[Plasma- and tissue concentrations following intramuscular administration of etofenamat. Pharmacokinetics of etofenamat and flufenamic acid in plasma, synovium, and tissues of patients with chronic polyarthritis after administration of an oily solution of etofenamat].

Studies on Plasma and Tissue Concentrations of Etofenamate following Intramuscular Application/Pharmacokinetics of etofenamate and flutenamic acid in plasma, synovia and tissues of patients with chronic polyarthritis after application of oily etofenamat solution Pharmacokinetics of etofenamate (ETO, CAS 30544-47-9; Rheumon i.m.) and flufenamic acid (FLU, CAS 530-78-9) were investigated in plasma, synovial fluid, and tissues after single intramuscular application of etofenamate to patients with rheumatoid arthritis. 62 patients with indicated operative procedure in the knee-joint received a single dose of etofenamate dissolved in oil before operation. At definite times between 1.5 and 48 h post injectionem samples from 6 patients of each time group were collected. Samples of plasma, synovial fluid, synovial membrane, muscle, bone, hyaline cartilage, and fat tissue and in some cases meniscus cartilage were taken. Concentrations of ETO and its active metabolite, FLU, were determined by HPTLC. In all tissues investigated, concentration/time courses of ETO and FLU were observed. ETO and FLU were measured first in all matrices 1.5 h at the latest 3 h post injectionem. Pharmacokinetics in tissues follows that in plasma. Rate-limiting step is the liberation of drug from the oil depot. For a long period pharmacokinetics of ETO and FLU is mainly determined by the constant liberation from the oil depot (zero order kinetics of liberation). Zero order kinetics is deduced from the linear ascent of the cumulated AUC (in percent) vs. time plot. It is directly related to the liberation of drug from the galenical formulation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

B cell tolerance in mice transgenic for anti-CD8 immunoglobulin mu chain.

To analyze in vivo the induction of B cell tolerance against a T cell surface antigen, we generated transgenic mice expressing an anti-CD8.2 mu heavy chain gene. We show that self-specific B cells are efficiently tolerized if they express the membrane-bound form of the transgenic mu chain on their surface but that they can escape tolerization if they express only the secreted form. In the latter, we find an enhanced expression of anti-CD8.2 antibodies after polyclonal B cell activation. As a result, transgenic anti-CD8.2 antibodies bind to the CD8+ T cells but they did not induce their elimination. Furthermore, we observed the preferential expression of a limited subset of endogenous light chains with the transgenic mu chain. This suggests a positive or negative selection for particular heavy and light chain combinations in B lymphocytes.

Animals↗
PubMed1991

Differentiation of lactococci by rRNA gene restriction analysis.

Strains of the subspecies of Lactococcus lactis could be differentiated by rRNA gene restriction fragment length polymorphisms (RFLP). 16S rRNA-specific oligonucleotide as well as polynucleotide DNA probes were used for the detection of restriction fragments. In addition, a site-specific probe was designed for the intergenic spacer region of 23S and 5S rRNA genes. For all lactococcal strains the putative presence of six rRNA operons was confirmed. A non-radioactive hybridization assay was used based on hybrid detection by chemiluminescence. Specific patterns were found for any of the strains investigated. Subspecies-specific restriction fragments could be identified in addition to the strain-specific patterns.

Base Sequence↗
PubMed1991

A differentially expressed murine RNA encoding a protein with similarities to two types of nucleic acid binding motifs.

Using differential screening, a murine cDNA, termed X16, was isolated corresponding to an mRNA which is more strongly expressed in pre-B cell lines relative to mature B-cell lines. The complete coding sequence of the mRNA predicts a 19kD protein with two domains connected by a proline-rich spacer. The N-terminal domain of about 90 amino acids encodes an RNA binding motif including the ribonucleoprotein consensus octapeptide found in one class of RNA-binding proteins and highly conserved from yeast to man. Within the very basic C-terminal domain of about 60 amino acids, several copies of two different peptides are found which are also present in several proteins which bind DNA or RNA. The expression of X16 is not limited to the lymphoid lineage. In adult mice, although the strongest expression was seen in thymus, mRNA was also found in testis, brain, spleen, and very low in heart. X16 mRNA was not detected in liver and kidney. In tissue culture, the expression of X16 mRNA can be induced by serum. The conserved protein motifs and expression pattern suggest that X16 could be involved in RNA processing correlating with cellular proliferation.

Amino Acid Sequence↗
PubMed1991

Expression and biological effects of high levels of serum IgE in epsilon heavy chain transgenic mice.

We have generated and examined transgenic mice carrying a rearranged immunoglobulin transgene coding for the heavy chain of an IgE antibody. These mice produce the secreted form of the recombinant epsilon heavy chain. Serum IgE levels were increased at least 100-fold over control values. Transgenic epsilon mRNA was detected in spleen and thymus, not in liver and heart. Transgenic epsilon production in vitro was slightly up-regulated by T cells, but not affected by interleukin 4 in vitro or Nippostrongylus infestation in vivo. The B cell and T cell compartments and antigen-specific IgE, IgG1 and IgM responses as well as the increase in endogenous IgE after Nippostrongylus infestation in transgenic mice were normal. These data indicate that the presence of high levels of transgenic IgE did not induce class-specific suppressive mechanisms. Transgenic IgE bound to Fc epsilon receptor type I and Fc epsilon receptor type II and mediated histamine release from mast cells in vitro and an allergic skin reaction in vivo. It inhibited an ovalbumin-specific skin reaction in ovalbumin-immunized transgenic mice only during the initial phases of the immune response. This result has a bearing on the feasibility of immune therapy of allergic diseases with substances that block binding of IgE to its receptors.

Age Factors↗
PubMed1991

The genes for a mouse hematopoietic differentiation marker called the heat-stable antigen.

We have isolated a murine cDNA by virtue of its expression in pre-B cell lines but not in plasmacytomas. In mouse, mRNA is detected by Northern blot analysis exclusively in hematopoietic tissues with the exception of brain. When expressed in bacteria, the encoded protein is specifically recognized by several antibodies against the murine hematopoietic differentiation marker called heat-stable antigen (HSA). In contrast to previous speculations, these results suggest that the antigenic determinant recognized by anti-HSA antibodies is proteinaceous. The cDNA sequence is essentially identical to a mouse HSA cDNA recently published (Kay et al., J. Immunol. 1990. 145: 1952). Three HSA genes were isolated, one of which corresponds to the isolated cDNA. The other two appear to be intronless retroposons which, despite numerous sequence changes, maintain an open reading frame. One of these intronless genes could code for an alternative form of HSA with a transmembrane domain and a cytoplasmic tail not encoded by the intron-containing gene. This gene could be expressed, based on sequence comparisons of the three genes. However, using polymerase chain reaction amplification of first strand cDNA from various cell lines and adult mouse tissues, we could detect expression only of the intron-containing gene.

Animals↗
PubMed1991

Molecular requirements for the mu-induced light chain gene rearrangement in pre-B cells.

During B cell differentiation rearrangement of immunoglobulin (Ig) genes is partially regulated by the Ig proteins. Rearrangement of heavy (H) chain genes is inhibited, whilst that of light (L) chain genes is induced by the membrane form of the mu H chain. In order to analyse additional structural requirements of mu induced L chain gene rearrangement we transfected wild-type mu and mutant mu constructs lacking functional exons encoding the first or second constant domains into Abelson murine leukemia virus (AMuLV) transformed pre-B cells. All mu chains are expressed on the surface of the pre-B cell and all associate with omega and iota, two proteins forming a surrogate light chain, necessary for mu membrane expression. Nevertheless, only wild-type mu and not the mutant mu proteins promote L gene rearrangement. A heterodimer of proteins with Mr of 33 kd and 36 kd was found associated with wild-type but not with the mutant mu proteins. Continuous presence of mu is required for L chain gene recombination since loss of mu stopped and readdition of mu started L gene rearrangement. We propose that the protein complex composed of mu and the 33 kd/36 kd protein heterodimer is responsible for the activation of the L chain gene locus and its rearrangement.

Animals↗
PubMed1991

First experience with a modified Siemens Lithostar shock wave system.

A Siemens Lithostar shock wave system was modified and investigated clinically. The modified system yields increased focal pressure and energy density. The first clinical experience in renal calculi shows a significant reduction in shock wave numbers per treatment. Higher energy output enables better treatment results for difficult stones such as staghorn and infections calculi. Despite the higher energy output more than 90% of treatments could be performed without anesthesia or analgesia. No significant side effects could be detected. The service life of the modified shock wave system increased by a factor of two.

Ceramics↗
PubMed1991

Fundamentals for the development of a lithotripter of the new generation. A survey of the principle knowledge and skills contributing to the progress in lithotripter efficiency for a wide scale of application.

An improved shock wave source is required for the extended application of extracorporeal lithotripsy in proven and anticipated novel fields of therapy. Fundamental research was performed in the domains: disintegration efficiency; hydrophone stability; absolute calibration, and source optimization. The combined experiences resulted in the development of a new shock wave source, the Siemens Electromagnetic Acoustic Source (EMAS-C), with considerably improved performance. The compact EMAS-C provides shock wave foci varying over a broad energy range, dedicated to efficient concrement disintegration and to new fields of application in medical therapy.

Calibration↗
PubMed1990

Partial tolerance in beta-galactosidase-transgenic mice.

A transgenic mouse line was produced which allowed the expression of E. coli beta-galactosidase (beta-Gal) under the regulatory elements of the immunoglobulin heavy chain locus. Expression of the transgene is found in spleen and bone marrow. Upon immunization of the transgenic mice with beta-Gal, a reduced but clearly detectable antibody response was obtained. Affinity purification with sera from immunized transgenic mice suggests that they contain lower affinity antibodies as compared to normal littermates. Transgenic and nontransgenic mice immunized with bovine serum albumin (BSA) alone or as a mixture with beta-Gal gave comparable anti-BSA responses. Immunization with a chemically cross-linked (Gal-BSA)-protein, however, showed a 10- to 30-fold difference in the anti-BSA response. Partial unresponsiveness to beta-Gal in the transgenic mice is best explained by a dominant, peripheral suppression mechanism linked to the antigen-presenting potential of B cells.

Animals↗