Through the labyrinth. The twists and turns of brain injury.
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Female↗
Biomedical subjects
M Eck
Publications and source records attributed to M Eck.
Evaluation of Helicobacter pylori in gastric MALT-type lymphoma: differences between histologic and serologic diagnosis.
Helicobacter pylori provides the pathogenic background for the development of gastric MALT-type lymphoma. The assessment of H. pylori is limited by the accuracy of the detection method used. Especially in patients with low-grade MALT-type lymphoma, the H. pylori status is the crucial question for therapeutic management. In this study, 60 patients with gastric MALT-type lymphoma. (lowgrade, 22; high-grade, 38) were investigated for the presence of H. pylori by histologic and serologic means. In 98% of the patients with MALT-type lymphoma, H. pylori-specific IgG serum antibodies were detected. In contrast, on histologic examination, H. pylori was found only in 78% of the patients (low-grade, 77%; high-grade, 79%). In this study, a discrepancy between serologic and histologic evaluation of the H. pylori status in gastric MALT-type lymphoma was found. Therefore, a H. pylori eradication therapy in low-grade MALT-type lymphoma, which often leads to a complete tumor regression, should not be excluded as a first line therapy because of a negative H. pylori status on histologic examination.
Antibodies, Bacterial↗
'Mass-murder' of ORFs from three regions of chromosome XI from Saccharomyces cerevisiae.
The complete sequence of the yeast Saccharomyces cerevisiae reveals the presence of many new genes, many of which are without homologs in databases. Characterisation of these genes by novel methods includes systematic deletion followed by phenotypic analysis of mutant strains. We have developed a hierarchical strategy for such a functional analysis of genes, in which the primary phenotypic screening is performed on groups of contiguous genes which are then reinvestigated down to the single gene level. This strategy is applied to the whole chromosome XI as part of EUROFAN (the EUROpean Functional ANalysis) program, and we present here our results on a group of 22 genes from this chromosome. This sample is representative of the results that are emerging for the whole chromosome. Out of the 22 genes deleted, three were shown to be essential, and another three genes confer a mutant growth phenotype to cells when deleted. All phenotypes have been complemented. These figures are in accordance with the previously published fraction of lethal and growth-defective deletions of single genes. We have found no synthetic phenotypes resulting from a combination of deleted genes and have always been able to attribute a mutant phenotype to a single gene.
Chromosomes↗
Activation of the protein tyrosine phosphatase SHP2 via the interleukin-6 signal transducing receptor protein gp130 requires tyrosine kinase Jak1 and limits acute-phase protein expression.
Stimulation of the interleukin-6 (IL-6) signalling pathway occurs via the IL-6 receptor-glycoprotein 130 (IL-6R-gp130) receptor complex and results in the regulation of acute-phase protein genes in liver cells. Ligand binding to the receptor complex leads to tyrosine phosphorylation and activation of Janus kinases (Jak), phosphorylation of the signal transducing subunit gp130, followed by recruitment and phosphorylation of the signal transducer and activator of transcription factors STAT3 and STAT1 and the src homology domain (SH2)-containing protein tyrosine phosphatase (SHP2). The tyrosine phosphorylated STAT factors dissociate from the receptor, dimerize and translocate to the nucleus where they bind to enhancer sequences of IL-6 target genes. Phosphorylated SHP2 is able to bind growth factor receptor bound protein (grb2) and thus might link the Jak/STAT pathway to the ras/raf/mitogen-activated protein kinase pathway. Here we present data on the dose-dependence, kinetics and kinase requirements for SHP2 phosphorylation after the activation of the signal transducer, gp130, of the IL-6-type family receptor complex. When human fibrosarcoma cell lines deficient in Jak1, Jak2 or tyrosine kinase 2 (Tyk2) were stimulated with IL-6-soluble IL-6R complexes it was found that only in Jak1-, but not in Jak 2- or Tyk2-deficient cells, SHP2 activation was greatly impaired. It is concluded that Jak1 is required for the tyrosine phosphorylation of SHP2. This phosphorylation depends on Tyr-759 in the cytoplasmatic domain of gp130, since a Tyr-759-->Phe exchange abrogates SHP2 activation and in turn leads to elevated and prolonged STAT3 and STAT1 activation as well as enhanced acute-phase protein gene induction. Therefore, SHP2 plays an important role in acute-phase gene regulation.
Antigens, CD↗
[Diagnostic value of stomach biopsy in comparison with surgical specimen in gastric B-cell lymphomas of the MALT type].
Diagnostic und therapeutic management of gastric lymphomas of the mucosa-associated lymphoid tissue type (MALT-type lymphomas) is often based exclusively on the evaluation of biopsy material. To evaluate the diagnostic value of gastric biopsies in gastric MALT-type lymphomas, biopsies--on average six per patient--and subsequent surgical specimens of 64 patients were compared at the Institute of Pathology, University of Würzburg. Tumor diagnosis and tumor gradind were assessed. Using biopsy specimens, primary gastric MALT-type lymphomas were correctly diagnosed by local pathologists in 69% of cases, but correctly graded as low-grade, high-grade or secondary high-grade lymphomas in only 41%. When immunohistochemistry and molecular biological techniques were applied in addition to conventional histology, diagnosis of gastric MALT-type lymphoma was achieved in biopsies in 95% of cases at the Institute of Pathology Würzburg, but correct grading in only 73%. In secondary high-grade MALT-type lymphomas, both components--the high-grade and the low-grade component--were identified in gastric biopsies in only 33% of cases. Diagnostic accuracy in gastric lymphomas based on biopsies is limited by biopsy artefacts, but improved by using immunohistochemistry and molecular biological techniques. Particularly in secondary high-grade MALT-type lymphomas the correct diagnosis is often missed when using biopsies, due to a low number of biopsy specimens.
Biomarkers, Tumor↗
Impaired secretion of very low density lipoprotein-triglycerides by apolipoprotein E- deficient mouse hepatocytes.
To explore mechanisms underlying triglyceride (TG) accumulation in livers of chow-fed apo E-deficient mice (Kuipers, F., J.M. van Ree, M.H. Hofker, H. Wolters, G. In't Veld, R.J. Vonk, H.M.G. Princen, and L.M. Havekes. 1996. Hepatology. 24:241-247), we investigated the effects of apo E deficiency on secretion of VLDL-associated TG (a) in vivo in mice, (b) in isolated perfused mouse livers, and (c) in cultured mouse hepatocytes. (a) Hepatic VLDL-TG production rate in vivo, determined after Triton WR1339 injection, was reduced by 46% in apo E-deficient mice compared with controls. To eliminate the possibility that impaired VLDL secretion is caused by aspecific changes in hepatic function due to hypercholesterolemia, VLDL-TG production rates were also measured in apo E-deficient mice after transplantation of wild-type mouse bone marrow. Bone marrow- transplanted apo E-deficient mice, which do not express apo E in hepatocytes, showed normalized plasma cholesterol levels, but VLDL-TG production was reduced by 59%. (b) VLDL-TG production by isolated perfused livers from apo E-deficient mice was 50% lower than production by livers from control mice. Lipid composition of nascent VLDL particles isolated from the perfusate was similar for both groups. (c) Mass VLDL-TG secretion by cultured apo E-deficient hepatocytes was reduced by 23% compared with control values in serum-free medium, and by 61% in the presence of oleate in medium (0. 75 mM) to stimulate lipogenesis. Electron microscopic evaluation revealed a smaller average size for VLDL particles produced by apo E-deficient cells compared with control cells in the presence of oleate (38 and 49 nm, respectively). In short-term labeling studies, apo E-deficient and control cells showed a similar time-dependent accumulation of [3H]TG formed from [3H]glycerol, yet secretion of newly synthesized VLDL-associated [3H]TG by apo E-deficient cells was reduced by 60 and 73% in the absence and presence of oleate, respectively. We conclude that apo E, in addition to its role in lipoprotein clearance, has a physiological function in the VLDL assembly-secretion cascade.
Animals↗
Human recombinant apolipoprotein E redirects lipopolysaccharide from Kupffer cells to liver parenchymal cells in rats In vivo.
Chylomicrons have been shown to protect mice and rats against a lethal dose of lipopolysaccharide and may serve as a therapeutic means to protect against endotoxemia. However, the requisite of isolation from human lymph hampers pharmaceutical application. Recently, we developed recombinant chylomicrons from commercially available lipids and human recombinant apolipoprotein E. The current study explored the effectiveness of these apoE-enriched emulsions in redirecting LPS from Kupffer cells to liver parenchymal cells. Upon injection into rats, 125I-LPS rapidly and specifically associated with the liver (64.3+/-3.1% of the injected dose) and spleen (4.1+/-0.7%). The uptake of LPS by the spleen was four- to fivefold reduced upon incubation with the apoE-enriched emulsion or free apoE (P < 0.0001), but not with emulsion alone or Lipofundin. Within the liver, 125I-LPS mainly associated with Kupffer cells. The uptake by Kupffer cells was eight- to ninefold reduced by the apoE-enriched emulsion or apoE alone (P < 0.01), and a 19.6-fold increased uptake ratio by liver parenchymal cells over Kupffer cells was observed. The emulsion without apoE had no effect on the in vivo kinetics of LPS. LPS interacted selectively with the apoE moiety of the recombinant chylomicron. Emulsion-associated and free apoE bound approximately two molecules of LPS, possibly by its exposed hydrophilic domain involving arginine residues. We anticipate that the protecting effect of endogenous chylomicrons against LPS-induced endotoxemia may result from the apoE moiety and that human recombinant apoE may serve as a therapeuticum to protect against endotoxemia.
Animals↗
MALT-type lymphoma of the stomach is associated with Helicobacter pylori strains expressing the CagA protein.
BACKGROUND & AIMS: Helicobacter pylori is considered to be involved in the pathogenesis of gastric lymphoma of mucosa-associated lymphoid tissue (MALT) type. Strains expressing the CagA protein (CagA+ strains) have been strongly associated with severe gastritis, duodenal ulceration, and gastric adenocarcinoma. The aim of this study was to determine the presence of H. pylori as well as incidence of CagA+ strains in gastric MALT-type lymphoma. METHODS: Sera of 68 patients with gastric MALT-type lymphoma (22 with low grade, 36 with high grade, and 10 with secondary high grade) were obtained, and the serological response to CagA was studied by immunoblotting using a purified recombinant CagA protein, a CagA+ strain, and the corresponding isogenic CagA- mutant. RESULTS: Of the patients with MALT-type lymphoma, 98.5% (67 of 68 patients) were H. pylori seropositive. In the only seronegative patient, the bacterium was detected histologically by Warthin-Starry staining. Of the seropositive patients, 95.5% had serum immunoglobulin G antibodies to CagA compared with 67% of an H. pylori-positive control group (33 of 49 patients; P = 0.000037) with chronic active gastritis. CONCLUSIONS: These results indicate infection of almost all patients with MALT-type lymphoma by CagA+ H. pylori strains. Strains expressing the CagA protein seem to play a crucial role in the pathogenesis of gastric MALT-type lymphoma.
Adult↗
Invasion and destruction of mucosal plasma cells by Tropheryma whippelii.
Whipple's disease is a poorly understood systemic disorder associated with the bacillus, Tropheryma whippelii. An early stage of Whipple's disease is studied by using electron microscopy (ELMI) and immunohistochemistry. The diagnosis was confirmed by polymerase chain reaction-amplification and sequencing of the 16S ribosomal-RNA of the bacterium. By using ELMI, Tropheryma whippelii was found in plasma cells and macrophages in the jejunal mucosa. The immunoglobulin (Ig)A-positive plasma cells were focally destructed and their number significantly reduced. However, the bacilli in the plasma cells were morphologically intact. In contrast, the macrophages showed no signs of cell destruction, but contained bacilli in various stages of disintegration. A cytopathic effect of Tropheryma whippelii to IgA plasma cells may be the reason for the commonly found plasma cell reduction in the small intestine mucosa and an important pathogenic mechanism contributing to the evasion of the bacilli from local immune response.
Actinobacteria↗
Active fulminant myocarditis characterized by T-lymphocytes expressing the gamma-delta T-cell receptor: a new disease entity?
Lymphocytic myocarditis is thought to be a virus-induced disease. T cells expressing the alpha-beta T-cell receptor seem to play a central role in the pathogenesis and to mediate tissue injury in this disease. A case of active fulminant myocarditis is described, which was analyzed by immunohistochemical, molecular biologic, and serologic methods. Infiltration of the heart tissue predominantly by gamma-delta T cells was detected by immunohistochemistry. No evidence of viral disease could be obtained by in situ hybridization with different enterovirus-specific DNA probes; by reverse-transcriptase polymerase chain reaction using specific primers for enteroviruses, adenoviruses, herpes simplex viruses, influenza A and B viruses, and cytomegaloviruses; or by enzyme-linked immunosorbent assay and electron microscopy. Because gamma-delta T cells may have an autoimmune capacity, we propose that these cells may trigger autoimmune myocarditis. These findings may be important in order to identify subgroups of patients who may benefit from immunosuppressive therapy.
Adult↗
Analysis of the physical properties and molecular modeling of Sec13: A WD repeat protein involved in vesicular traffic.
WD repeat proteins are a family of proteins that contain a series of highly conserved internal repeat motifs, usually ending with WD (Trp-Asp). The G beta subunit of heterotrimeric guanine nucleotide binding protein is a member of this family, and its crystal structure has been recently solved at high resolution (Wall et al. (1995) Cell 83, 1047-1058; Sondek et al. (1996) Nature 379, 369-374). Based on the coordinates of G beta, we have constructed a model for the structure of Sec13, a 33 kDa WD repeat protein from Saccharomyces cerevesiae essential for vesicular traffic. The model has been tested using a combination of biophysical and biochemical methods. Sec13 was expressed in Escherichia coli as a hexa-His-tagged protein (H6Sec13) and purified to homogeneity. In contrast to some other WD repeat proteins that are unable to fold into monomeric structures when expressed in E. coli, H6Sec13 was soluble and monomeric in the absence of detergent. The far-UV circular dichroism (CD) spectra of H6Sec13 indicated less than 10% alpha-helix consistent with the model which predicts primarily beta-sheets. H6Sec13 shows a cooperative and irreversible thermal denaturation curve consistent with a tightly packed structure. The CD spectrum shows an unusual positive ellipticity at 229 nm that was attributed to interactions of surface tryptophans since the 229 nm maximum could be abolished by modification of 6.3 +/- 0.3 (n = 3) tryptophans (out of 15 total in the molecule) with N-bromosuccinimide. Our model predicts that three sets of tryptophans are clustered near the surface. As predicted by the model, purified H6Sec13 was completely resistant to trypsin digestion. The concordance of the model of Sec13 presented in this paper with the biochemical and biophysical studies suggests that this model can be useful as a guide to further experiments designed to elucidate the function of Sec13 in vesicular traffic.
Amino Acid Sequence↗
Antigastric autoantibodies in Helicobacter pylori gastritis: prevalence, in-situ binding sites and clues for clinical relevance.
Colonization of human gastric mucosa with Helicobacter pylori leads to chronic active gastritis and induces the occurrence of an acquired mucosa-associated lymphoid tissue (MALT) in the stomach. This remodelling of the gastric mucosa together with chronic antigen persistence may induce autoimmune reactions. The aim of this study was to investigate humoral autoimmune reactions to human gastric mucosa in H. pylori gastritis and their clinical relevance. Sera from patients with dyspeptic symptoms were tested for presence of IgG immunoglobulins against H. pylori. Gastric infection with H. pylori and alterations of gastric mucosa were demonstrated by histological examination of gastric biopsy specimens. All sera were tested for reactivity against human gastric mucosa by immunohistochemistry. Two different in-situ binding sites of antigastric autoantibodies were observed. Binding to canalicular structures within parietal cells was significantly correlated with antibodies to H. pylori, elevated basal gastrin levels and atrophy of gastric corpus glands. Our data indicate that autoimmune reactions to antigens in the human gastric mucosa occur in H. pylori gastritis and that they may play a role in the pathogenesis of the disease.
Adult↗
[Hybridomas as tools for research on MALT type lymphomas].
The antigen receptor of the MALT lymphoma cells provides crucial information, which may help to elucidate the pathogenesis of that tumor. Therefore hybridomas were produced from five MALT type lymphomas. The identity was proven by sequencing the VH chain of the tumor and the hybridomas. It could be shown the one step of subcloning and limiting dilution is necessary to obtain a monoclonal hybridoma in most cases. So it is indispensable to check the identity of the tumor antibody and the hybridoma antibody for each hybridoma. Otherwise it may be possible that bystander cells infiltrating the tumor, but not belonging to the malignant clone, get fused. Furthermore we provide evidence of an intra tumoral diversity within the MALT type lymphoma that was reflected by the different mutation pattern of the tumor derived hybridomas. Therefore the hybridomas are allowing investigation on the protein level about the hypermutation of the genes of the MALT lymphoma antibodies and the possible role antigenic selection within the tumor.
Base Sequence↗
Effects of postnatal blockage of cortical activity with tetrodotoxin upon lesion-induced reorganization of vibrissae-related patterns in the somatosensory cortex of rat.
Previous studies have shown that postnatal blockade of thalamocortical activity with either tetrodotoxin (TTX) or the NMDA receptor antagonist DL-2-amino-5-phosphonovalerate (APV) does not prevent the formation of vibrissae-related patterns. In the present study, blockade of cortical activity with TTX was combined with ablation of a row of vibrissae follicles or transection of the infraorbital nerve (ION, the trigeminal nerve branch that supplies the vibrissae follicles) to determine whether the cortical reorganization that follows these lesions in otherwise untreated animals was dependent upon neuronal activity that could be blocked with TTX. The results demonstrated that cortical TTX implants had no quantitative or qualitative effects upon the cortical reorganization that followed either vibrissae follicle cauterization or ION transection.
2-Amino-5-phosphonovalerate↗
Effects of postnatal blockade of cortical activity with tetrodotoxin upon the development and plasticity of vibrissa-related patterns in the somatosensory cortex of hamsters.
Several previous studies have shown that postnatal blockade of thalamocortical activity with either tetrodotoxin (TTX) or the N-methyl-D-aspartate (NMDA) receptor antagonist D,L-2-amino-5-phosphonovalerate (APV) does not prevent the formation of vibrissa-related patterns in the primary somatosensory cortex of rats. One limitation of these studies is that this pattern forms very shortly after birth in rats, and there may be only a very limited time over which it may be influenced by activity blockade. In the present study, the effect of activity blockade was evaluated in a more altricial rodent, the hamster. The present study showed that a pattern of thalamocortical afferents corresponding to the vibrissae is not observed until the fourth postnatal day in hamsters. Nevertheless, application of TTX-impregnated implants to the cortices of newborn hamsters had no qualitative or quantitative effect upon vibrissa-related patterns in the primary somatosensory cortices of these animals. Moreover, TTX implants did not prevent the changes in patterns that followed cauterization of a row of vibrissa follicles.
Afferent Pathways↗
Peripheral influences on the size and organization of somatotopic representations in the fetal rat cortex.
Nerve lesions at different fetal ages and on the day of birth were used to determine the role of the periphery in establishing territories devoted to representations of different portions of the body surface in rat somatosensory cortex. Transection of the infraorbital nerve (ION), the trigeminal branch that supplies the whisker pad, resulted in a significant reduction in the area within the primary somatosensory cortex devoted to the representation of the mystacial vibrissae in fetal, but not newborn, rats. Such lesions in fetal, but not neonatal, rats also resulted in significant increases in the cortical area devoted to the representation of the lower lip and jaw. There was a significant positive correlation between the reduction in the vibrissae representation and the expansion of that of the lower lip and jaw. Damage to the ION in either neonatal or fetal rats failed to increase significantly the amount of cortex devoted to the representation of the forepaw. These results indicate that the primary afferent innervation of the periphery does influence the amounts of cortex devoted to representations of different parts of the body surface and that the representation of one region can expand significantly when that of another body part is reduced.
Animals↗
Role of acidic amino acids in the allosteric modulation by gallamine of antagonist binding at the m2 muscarinic acetylcholine receptor.
The purpose of this study was to explore the role of acidic amino acids in the allosteric behavior of gallamine at the m2 receptor. This was achieved by first mutating the acidic residues to neutral residues by site-directed mutagenesis. Both the parent and mutated receptors were expressed in mouse fibroblast A9L cells and characterized pharmacologically. The two main methods used were (i) Schild analysis of equilibrium binding data and (ii) study of the effect of gallamine on the dissociation kinetics of N-methylscopolamine. The Schild analysis gave an estimate of the affinity of gallamine for the allosteric site (KdA) and also a measure of the level of cooperativity (alpha) between the allosteric and primary binding sites. For the receptors studied, a good agreement was found between the alpha KdA values calculated from the Schild analysis and the IC50 values for the effect of gallamine on the N-methylscopolamine off-rate. One mutated receptor, in which the acidic EDGE (Glu-Asp-Gly-Glu) sequence of the putative third outer domain was changed to the neutral LAGQ (Leu-Ala-Gly-Gin) sequence, displayed an 8-fold reduction in affinity for gallamine at the allosteric site, in comparison with the parent receptor. The level of cooperatively between the allosteric and primary binding sites in this mutant was 46% of that of the parent receptor. A second mutated receptor, in which Asp-97 (near the top of putative transmembrane domain 3) was changed to asparagine, was found to have a level of cooperativity between sites 58% of that of the parent but was found not to be affected with respect to the affinity of gallamine for the allosteric site. When all of the acidic groups on the outer side were changed to neutral residues, there was still only an 8.6-fold reduction in gallamine affinity for the allosteric site, but the level of cooperativity was reduced to 19% of that found in the parent receptor. The results suggest that the allosteric site for gallamine binding in the m2 receptor residues at or near the putative third outer domain and that both the EDGE motif and Asp-97 play an essential role in the interaction between the two sites. However, none of the acidic amino acids mutated were found to be critical for binding at the allosteric site.
Allosteric Regulation↗
[Development and evaluation of a program for preventing sexual abuse in the preschool age].
The present study reports on the development and evaluation of an intervention program to prevent sexual abuse in the preschool age. The main aim of the program is to increase the social competencies of preschool children. Starting from critiques at existing prevention programs an intervention adapted at the cognitive abilities of preschool children was developed. The central themes of the program are the abilities to deal with feelings, touches, secrets, saying no, and getting support. The program effects were tested by an experimental study. Subjects were 80 preschool children aged 4 to 6 years. Forty children participated at the program while the other children served as control group. The results show clear increases of knowledge on all program dimensions which were stable over an interval of at least two months. The implications of the results for the use of prevention programs for sexual abuse in the preschool age are evaluated and discussed.
Child Abuse, Sexual↗