Showing papers by "University of Cologne published in 1987"

The precursor of Alzheimer's disease amyloid A4 protein resembles a cell-surface receptor

Abstract: Alzheimer's disease is characterized by a widespread functional disturbance of the human brain. Fibrillar amyloid proteins are deposited inside neurons as neurofibrillary tangles and extracellularly as amyloid plaque cores and in blood vessels. The major protein subunit (A4) of the amyloid fibril of tangles, plaques and blood vessel deposits is an insoluble, highly aggregating small polypeptide of relative molecular mass 4,500. The same polypeptide is also deposited in the brains of aged individuals with trisomy 21 (Down's syndrome). We have argued previously that the A4 protein is of neuronal origin and is the cleavage product of a larger precursor protein. To identify this precursor, we have now isolated and sequenced an apparently full-length complementary DNA clone coding for the A4 polypeptide. The predicted precursor consists of 695 residues and contains features characteristic of glycosylated cell-surface receptors. This sequence, together with the localization of its gene on chromosome 21, suggests that the cerebral amyloid deposited in Alzheimer's disease and aged Down's syndrome is caused by aberrant catabolism of a cell-surface receptor.

The strychnine-binding subunit of the glycine receptor shows homology with nicotinic acetylcholine receptors.

Abstract: We have cloned and sequenced cDNAs of the strychnine-binding subunit of the rat glycine receptor, a neurotransmitter-gated chloride channel protein of the CNS. The deduced polypeptide shows significant structural and amino-acid sequence homology with nicotinic acetylcholine receptor proteins, indicating that there is a family of genes encoding neurotransmitter-gated ion channels.

Gene structure and extracellular secretion of Neisseria gonorrhoeae IgA protease

Abstract: Several human bacterial pathogens, including the Gram-negative diplococcus Neisseria gonorrhoeae, produce extracellular proteases that are specific for human immunoglobulin IgA1, (refs 1, 2). Immunoglobulin A (IgA) proteases have been studied extensively and the genes of some species cloned in Escherichia coli3–7, but their role in pathogenesis remains unclear8. Recently we derived a DNA fragment of 5 kilobases (kb) from N. gonorrhoeae MS 11 directing extracellular active enzyme in E. coli4. Although the mature enzyme of strain MS 11 was shown to have a relative molecular mass of 106,000 (Mr 106K) in gels4, the DNA sequence of this cloned fragment reveals a single gene coding for a 169K precursor of IgA protease. The precursor contains three functional domains, the amino-terminal leader which is assumed to initiate the inner membrane transport of the precursor, the protease, and a carboxyl-terminal 'helper' domain apparently required for extracellular secretion (excretion). Based on the structural features of the precursor, we propose a model in which the helper serves as a pore for excretion of the protease domain through the outer membrane. IgA protease acquires an active conformation as its extracellular transport proceeds and is released as a proform from the membrane-bound helper by autoproteolysis. The soluble proform further matures into the 106 K IgA protease and a small stable α-protein.

Evolutionary and somatic selection of the antibody repertoire in the mouse

Abstract: The repertoire of antibody variable (V) regions has been subject to evolutionary selection, affecting both the diversity of V region genes in the germline and their expression in the B lymphocyte population and its subsets. In ontogeny, contact with an antigen leads to the expansion of B cells expressing antibodies complementary to it. In a defined phase of B cell differentiation, new sets of V regions are generated from the existing repertoire through somatic hypermutation. Cells carrying advantageous antibody mutants are selected into the memory compartment and produce a stable secondary response upon reexposure to the antigen.

Expansion and functional activity of Ly‐1+ B cells upon transfer of peritoneal cells into allotype‐congenic, newborn mice

Abstract: Transfer of peritoneal cells from adult donors into newborn, allotype-congenic mice led to colonization of the recipient mice by donor-derived B lymphocytes expressing the Ly-1 surface marker (Ly-1 B cells). These cells not only persisted in the recipient mice for at least 5 months, but also increased in number. In contrast, bone marrow-derived stem cells did not or scarcely give rise to B cells after intraperitoneal injection into congenic newborn recipients under the same experimental conditions. Approximately half of the IgM in the serum of peritoneal cell-recipients was produced by donor-derived Ly-1 B cells, suggesting that high levels of serum IgM in a normal mouse are produced by this B cell subpopulation. The transferred Ly-1 B cells were able to respond in a normal fashion to alpha (1----3)dextran, but they did not participate in thymus-dependent and -independent (TI II) immune responses to the hapten (4-hydroxy-3-nitrophenyl)acetyl (NP). In neither the immune response to alpha (1----3)dextran nor that to NP were we able to detect an influence of the transferred Ly-1 B cells on the selection of the idiotypic repertoire in the recipient mice.

Failure of familial Alzheimer's disease to segregate with the A4-amyloid gene in several European families.

Abstract: The gene coding for the amyloid protein, a component of neuritic plaques found in brain tissue from patients with Alzheimer's disease, has been localized to chromosome 21, and neighbouring polymorphic DNA markers segregate with Alzheimer's disease in several large families. These data, and the association of Alzheimer's disease with Down's syndrome, suggest that overproduction of the amyloid protein, or production of an abnormal variant of the protein, may be the underlying pathological change causing Alzheimer's disease. We have identified a restriction fragment length polymorphism of the A4-amyloid gene, and find recombinants in two Alzheimer's disease families between Alzheimer's disease and the A4-amyloid locus. This demonstrates that the gene for plaque core A4-amyloid cannot be the locus of a defect causing Alzheimer's disease in these families. These data indicate that alterations in the plaque core amyloid gene cannot explain the molecular pathology for all cases of Alzheimer's disease.

Role of Staphylococcus protease in the development of influenza pneumonia

Abstract: In influenza the combined virus-bacterial pneumonia is approximately three times more common than primary viral pneumonia. The bacteria most commonly involved are Staphylococcus aureus, Streptococcus pneumoniae and Haemophilus influenzae. S. aureus co-infection is reported to have a fatality rate of up to 42% (ref. 2). It is thought that virus infection in the respiratory tract favours growth conditions for bacteria. In this letter data are presented which show that some S. aureus strains secrete a protease which exerts a decisive influence on the outcome of influenza virus infection in mice by cleavage activation of the virus haemagglutinin.

Timing, Genetic Requirements and Functional Consequences of Somatic Hypermutation during B‐Cell Development

Abstract: While somatic antibody mutants are rare in the preimmune repertoire and in primary immune responses, they dominate secondary and hyperimmune responses. We present evidence that somatic hypermutation is restricted to a particular pathway of B-cell differentiation in which distinct sets of B-cell clones are driven into the memory compartment. In accord with earlier results of McKean et al. (1984) and Rudikoff et al. (1984), somatic mutation occurs stepwise in the course of clonal expansion, before and after isotype switch, presumably at a rate close to 1 X 10(-3) per base pair per generation. At this rate, both selectable and unselectable mutations accumulate in the rearranged V region genes. The distribution of replacement mutations in the V regions shows that a fraction of the mutations in CDRs is positively selected whereas replacement mutations are counterselected in the FRs. By constructing an antibody mutant through site-specific mutagenesis we show that a point mutation in CDR1 of the heavy chain, found in most secondary anti-NP antibodies, is sufficient to increase NP binding affinity to the level typical for the secondary response. Somatic mutation may contribute to the immune repertoire in a more general sense than merely the diversification of a specific response. We have evidence that clones producing antibodies which no longer bind the immunizing antigen can be kept in the system and remain available for stimulation by a different antigen. Somatic mutations are 10 times less frequent in DJH loci than in either expressed or non-expressed rearranged VDJH or VJ loci. We therefore conclude that a V gene has to be brought into the proximity of the DJH segment in order to fully activate the hypermutational mechanism in these loci.

Activation of V kappa gene rearrangement in pre-B cells follows the expression of membrane-bound immunoglobulin heavy chains.

Abstract: During B cell development V kappa gene rearrangement seems to occur only in mu-positive pre-B cells. To study the role of the mu chain in the activation of the Ig kappa locus, we introduced expression vectors carrying different forms of the mu gene into null pre-B cells. The activation of the Ig kappa locus followed the expression of the membrane form (micron) of the mu chain. The expression of the secreted form (microS) did not result in the activation of the Ig kappa locus. We further show that both forms of the mu chain differ in their intracellular transport in pre-B cells.

Polyphosphorus Compounds—New Results and Perspectives

Abstract: In contrast to the numerous known and often technically important mono- and diphosphorus compounds with phosphorus in its maximum oxidation state, polyphosphorus compounds led only a shadowy existence up to about twenty years ago. One of the reasons for this was the properties of such compounds, which made their handling and structural characterization difficult. This problem was solved by the development of modern preparative techniques and, especially, by the further methodological development of nuclear magnetic resonance spectroscopy. Thus, a fascinating new branch of phosphorus chemistry has been opened up in recent years. The first comprehensive review on this subject was published five years ago. Since then, research on this “element-near” chemistry of phosphorus has produced further impressive advances with the result that a surprisingly large variety of compounds with skeletons consisting of chains or rings of phosphorus atoms is known today. However, the recent observation of the spontaneous formation of the “aromatic” pentaphosphacyclopentadienide ion, P, during the synthesis of phosphorus-richer polyphosphides from phosphorus-poorer compounds in solution and the discovery of the inversion of phosphorus in tetra- and pentacyclic organophosphanes demonstrate that this field is still capable of producing surprises.

Functional and morphological abnormalities in temporal lobe epilepsy: a comparison of interictal and ictal EEG, CT, MRI, SPECT and PET

Abstract: Ten patients suffering from drug-resistant complex partial seizures, with EEG abnormalities in the temporal region, were studied by means of non-invasive electrophysiological techniques (video-monitored, 16-channel, prolonged surface and sphenoidal EEG) as well as by imaging techniques (CT, MRI, SPECT and PET). Analysis of interictal and ictal EEG indicated the localization of epileptic activity in one side in eight cases. CT demonstrated focal abnormalities in three, SPECT in five unequivocally (in another four questionably, with the same lateralization as indicated by PET), MRI in eight, and PET in all cases. While only EEG provided specific diagnostic information, the focus definition was consistently good on PET images, poor on CT scans, and generally good but less consistent on MRI.

Phenotypic assay for excision of the maize controlling element Ac in tobacco.

Abstract: We describe a phenotypic assay designed to detect excision of the maize controlling element Ac from a selectable marker gene, neomycin phosphotransferase II (NPT II). An NPT II gene which expresses kanamycin resistance in tobacco cells, and contains a unique restriction enzyme site in the untranslated leader region, was constructed. Ac, or a defective Ac element (Ac big up tri, open), was inserted into the leader region of this gene. The transposon insertions inactivated the NPT II gene as determined by transient NPT II expression assays. The three plasmids were inserted into the T DNA of Agrobacterium tumefaciens Ti plasmid vectors, and transferred to tobacco protoplasts. The transformed protoplasts were selected with 100 or 200 microg/ml kanamycin. Protoplasts transformed by the NPT II gene interrupted by Ac formed 25% as many calli resistant to 100 or 200 microg/ml kanamycin as protoplasts transformed by the uninterrupted NPT II gene. Protoplasts transformed by the NPT II gene interrupted by Ac big up tri, open did not form any calli resistant to 200 microg/ml of kanamycin when transformed under similar conditions. Southern blot hybridization analyses of seven kanamycin-resistant calli or plants obtained after transformation by the NPT II gene interrupted by Ac revealed that in all cases Ac had excised, restoring the structure of the NPT II gene. This assay is therefore useful to monitor the activity of a transposable element such as Ac and to define the regions of this element involved in transposition activity.

The pattern of proliferation of the neuroblasts in the wild-type embryo of Drosophila melanogaster.

Abstract: The pattern of neuroblast divisions was studied in thoracic and abdominal neuromeres of wild-type Drosophila melanogaster embryos stained with a monoclonal antibody directed against a chromatin-associated antigen Since fixed material was used, our conclusions are based upon the statistical evaluation of a large number of accurately staged embryos, covering the stages between the formation of the cephalic furrow up to shortened germ band Our observations point to a rather stereotypic pattern of proliferation, consisting of several parasynchronous cycles of division The data suggest that all SI neuroblasts divide at least eight times, all SII neuroblasts six or seven times and all SIII neuroblasts at least five times This conclusion is based on the mapping of mitotic neuroblasts and is supported by the progressive reduction of the neuroblast volume and by the results of cell countings performed on embryos of increasing age No conclusive evidence was obtained concerning the fate of the neuroblasts after their last mitosis, ie it cannot be decided whether the neuroblasts degenerate or become incorporated as inconspicuous cells in the larval ventral cord The duration of the cycles of division of the neuroblasts was found to be 40–50 min each, while in the case of ganglion mother cells about 100 min are required to complete one cell cycle

Transcription of transposable element Activator (Ac) of Zea mays L

Abstract: Transcripts of various sizes hybridize to the transposable element Ac of Zea mays in most maize lines. A 3.5-kb mRNA with an abundance of 1–3 x 107 of the poly(A) RNA, however, is found exclusively in those lines that carry an active Ac. Plants with two Ac elements contain slightly more 3.5-kb Ac transcript than those with only one Ac. Overlapping cDNA clones spanning most of the message have been isolated and sequenced. The 5'-end of the transcript was determined by Northern hybridization and S1 mapping. It starts at several sites over a distance of nearly 100 bases, contains an AUG-free leader 600-700 nucleotides long, has a long open reading frame encoding 807 amino acids and an untranslated 3'-sequence of 239 nucleotides. Four introns with a combined length of 654 bases are removed from the primary transcript. Radiosequencing of in vitro translation products shows that translation of the long open reading frame begins at the first AUG, even though it is located in an unfavourable sequence context. The transcript is found in all organs investigated, provided an active Ac is present in the stock.

The interaction of the recognition helix of lac repressor with lac operator.

Abstract: We have constructed a system which allows systematic testing of repressor--operator interactions. The system consists of two plasmids. One of them carries a lac operon in which lac operator has been replaced by a unique restriction site into which synthetic operators can be cloned. The other plasmid carries the gene coding for the repressor, in our case a semisynthetic lacI gene of which parts can be exchanged in a cassette-like manner. A galE host allows us to select for mutants which express repressors with altered specificities. Here we report the change of specificity in the lac system by changing residues 1 and 2 of the recognition helix of lac repressor. The specificity changes are brought about cooperatively by the change of both residues. Exchanges of just one residue broaden the specificity. Our results hint that the recognition helix of lac repressor may possibly have the opposite orientation to those in Lambda cro protein or 434 CI repressor.

Pouch versus esophagojejunostomy after total gastrectomy: a randomized clinical trial.

Abstract: This is an interim report of a randomized clinical trial on esophagojeju-nostomy (EJ) versus Hunt-Lawrence-Rodino (HLR) pouch as reconstruction techniques following total gastrectomy and systematic lymphadenectomy for gastric cancer treatment. The randomized trial preceded a pilot study comparing the Longmire-Gutgemann interposition and the HLR. The pilot study included 7 patients, the randomized trial 38 patients (60 planned). The main outcome variables in the pilot study were food resorption, caloric intake, and body weight. Survival probability and general well-being (quality of life) were measured in the randomized trial. A score was composed of disease-specific and socio-personal variables with well-being ranging from 0 (worst) to 14 (best) points. Concerning food resorption in the pilot study, no relevant advantage of the duodenal passage was found. The main postoperative disorder was insufficient food intake. Despite a radical operation, a hospital mortality rate of 16%, and a complication rate of 37%, gastric cancer still has a poor prognosis. In the randomized trial only 15 (39%) of 38 patients were alive 1 year after operation, but the survival probability was higher (58%) after HLR than after EJ (24%) (p<0.05). Hunger and appetite were strongly reduced during the first 6 months after operation. Food intake was less than half of the preoperative values, which was reflected by an average decrease in body weight of 7 kg. Patients dying within the first year after total gastrectomy suffered an irreversible loss of quality of life (scoring 7 points). They had no objective benefit from the operation. Patients surviving this period regained quality of life and exceeded preoperative values, especially after HLR. We conclude that HLR-operated patients who have a chance of surviving for at least 1 year benefit from total gastrectomy in regard to quality of life. Cet article est consacre au bilan provisoire d'une etude clinique randomisee de l'oesophago-jejunostomie (EJ) par rapport a l'operation de Hunt-Lawrence-Rodino (HLR) comme technique de reconstruction apres gastrectomie totale et lymphadenectomie systematique pour cancer de l'estomac. Le bilan a ete etabli a partir d'une etude pilote comparant l'interposition Longmire-Gutgemann et la HLR. Cette premiere etude a porte sur 7 patients et le etude randomisee sur 38 patients (60 sont prevues). Dans l'etude pilote la reabsorption intestinale, le poids et l'absorption calorique furent les variables essentielles pour mesurer l'avenir des malades. Dans le etude randomisee la probabilite de survie et la qualite de la vie ont ete ajoutees. L'etat general a ete represente par un score comprenant des variables specifiques de la maladie et socio-personnelles allant de 0 (tres mal) a 14 (tres bien) points. Dans l'etude pilote le passage duodenal n'a pas montre d'avantage concernant la reabsorption intestinale. Le malaise post-operatoire essentiel a ete l'insuffisance de l'absorption calorique. L'operation radicale a une mortalite hospitaliere de 16% et comprend un taux de complication de 37%. Le cancer de l'estomac est de prognostic peu favorable. Seuls 15 (39%) des 38 patients ont survecu la premiere annee dans le etude randomisee mais la probabilite de survie apres HLR (58%) depasse celle apres EJ (24%) (p<0.05). La faim et l'appetit ont ete severement reduits pendant les 6 premiers mois post-operatoires. Comparee a la situation pre-operatoire, la quantitie de nourriture a diminue d'au moins 50% ce qui correspond a une perte de poids de 7 kilos en moyenne. Les malades qui ne survivent pas la premiere annee subissent une perte importante et irreversible de leur qualite de vie. Ceci nous amene a dire qu'ils ne profitent pas de l'intervention chirurgicale contraitement aux autres qui regagnent une qualite de vie egale ou meme superieure aux valeurs pre-operatoires. Au total nous pouvons affirmer que ce sont essentiellement les patients operes qui ont subi une HLR qui survivent un an ou plus et qui tirent profit de la gastrectomie totale.

Polyphosphorverbindungen – neue Ergebnisse und Perspektiven

Abstract: Polyphosphorverbindungen haben – im Gegensatz zu den zahlreichen bekannten und auch technisch wichtigen Mono- und Diphosphorverbindungen der maximalen Oxidationsstufe dieses Elementes – bis vor zwei Jahrzehnten ein Schattendasein gefuhrt. Ein Grund dafur waren die Eigenschaften dieser Verbindungen, die ihre Handhabung und strukturelle Charakterisierung erschwerten. Durch die Entwicklung moderner praparativer Arbeitstechniken und vor allem durch die methodische Weiterentwicklung der Kernresonanzspektroskopie liesen sich diese Probleme losen, so das in letzter Zeit ein faszinierendes neues Teilgebiet der Phosphorchemie erschlossen werden konnte, uber das erstmals vor funf Jahren zusammenfassend berichtet worden ist. Seitdem hat der Ausbau dieser „Element-nahen” Chemie des Phosphors weiterhin beeindruckende Fortschritte gemacht; heute ist eine erstaunliche Vielfalt von Verbindungen mit einem Gerust aus Phosphorketten oder -ringen bekannt. Das dieses Gebiet aber noch immer gut fur Uberraschungen ist, zeigt die jungst beim Aufbau von P-reicheren aus P-armeren Polyphosphiden in Losung beobachtete spontane Bildung des „aromatischen” Pentaphosphacyclopentadienid-Ions, P, ebenso wie die Entdeckung der Inversion des Phosphors bei tetra- und pentacyclischen Organophosphanen.

Unsharp particle-wave duality in a photon split-beam experiment

Abstract: In a quantum mechanical two-slit experiment one can observe a single photon simultaneously as particle (measuring the path) and as wave (measuring the interference pattern) if the path and the interference pattern are measured in the sense of unsharp observables. These theoretical predictions are confirmed experimentally by a photon split-beam experiment using a modified Mach—Zehnder interferometer.

Lineage analysis of transplanted individual cells in embryos of Drosophila melanogaster : IV. Commitment and proliferative capabilities of mesodermal cells.

Abstract: We describe the results of cell transplantation experiments performed to investigate mesodermal lineages in Drosophila melanogaster, particularly the lineages of the somatic muscles, the visceral muscles and the fat body. Cells to be transplanted were labelled by injecting a mixture of horseradish peroxidase (HRP) and fluorescein-dextran (FITC) in wild-type embryos at the syncytial blastoderm stage. For transplantation cells were removed from the ventral furrow, 8–12 min after the start of gastrulation, and individually transplanted into homotopic or heterotopic locations of unlabelled wild-type hosts of the same age. HRP labelling in the resulting cell clones was demonstrated histochemically in the fully developed embryo; histotypes could be distinguished without ambiguity. Mesodermal cells were already found to be committed to mesodermal fates at the time of transplantation. They developed only into mesodermal derivatives and did not integrate in non-mesodermal organs upon heterotopical transplantation. No evidence was found for commitment to any particular mesodermal organ at the time of transplantation. The majority of somatic muscle clones contributed cells to only one segment. However, clones were not infrequently distributed through two or even three segments. Clones of fat body cells were generally restricted to a small region. However, cells of clones of visceral musculature were widely distributed. With respect to the proliferative abilities of transplanted cells the clones were difficult to interpret due to the syncytial character of the somatic musculature and the fact that the organization of the other organs is poorly understood. Evidence from histological observations of developing normal embryos indicates only three mitoses for mesodermal cells. Clones larger than seven cells were not found when embryos were fixed previous to germ-band shortening; larger clones were found in the fat body and visceral musculature after fixing the embryos at the end of organogenesis. Quantitative considerations suggest that a few mesodermal cells might perform more than three mitoses.

Molecular analysis of the neurogenic locus Enhancer of split of Drosophila melanogaster

Abstract: Enhancer of split [E(spl)], one of the neurogenic loci of Drosophila, is located in bands 96F8-13. One hundred and fifty kilobases of genomic DNA, spanning the E(spl) locus, were cloned by chromosomal walking. DNA heterogeneities associated with eleven E(spl) mutations, including three Pr alleles, were mapped to a region of 36 kb, and an additional one outside of this region. One of these mutations is a deletion of ˜34 kb that causes severe neural hyperplasia of homozygous embryos with complete penetrance. Mutations associated with DNA polymorphisms mapping within smaller regions do not lead to a fully penetrant neurogenic phenotype. The 36-kb region encodes 11 major transcripts, which exhibit distinct temporal and/or spatial patterns of expression. The expression of one of these transcripts is modified in two different mutants. In addition, one of the mutants [E(spl)D] shows another transcript, which is not present in the wild-type and co-exists with the remaining transcripts. We suggest that more than one of the 11 transcripts are necessary for a normal function of the E(spl) locus. The spatial distribution of four of these RNAs, which exhibit almost identical patterns of expression, strongly suggests that the encoded proteins are required for the process of segregation of neural and epidermal lineages.

Genes in subdivision 1B of the Drosophila melanogaster X-chromosome and their influence on neural development

Abstract: Genes within subdivision IB of the X-chromosome of Drosophila melanogaster are known to affect the development of both the central (CNS) and the peripheral (PNS) embryonic nervous system. In this paper we describe the phenotypes of embryos hemizygous for terminal and interstitial deletions of region 1B1–1B10, and of embryos carrying different mutations in certain genes of this region. A minimum of 6 genetic functions that are involved in neural development can be defined in this region. Three of these genes, mapping to the I'sc (a gene of the achaete-scute complex, ASC), elav and md loci, affect major and apparently different aspects of CNS development. Two additional genes of the ASC, ac and sea, also play a role in CNS development, although their participation can only be demonstrated under certain conditions. Finally, in the rightmost part of the region uncovered by the deletion Df(1)260.1, two not yet well separated functions are found to be required for embryonic CNS and compound eye development, res...

Surface Width Exponents for Three- and Four-Dimensional Eden Growth

Abstract: By means of noise reduction we investigate the scaling behaviour of the surface width w of d-dimensional Eden clusters growing on flat substrates of linear extent L. We find that w scales for small average deposit height h as hβ, and in the steady state as Lα. Our results for d = 3 (α = 0.33 ± 0.01, β = 0.22 ± 0.02) and for d = 4 (α = 0.24 ± 0.02, β = 0.146 ± 0.015) support the scaling relation α(1 + 1/β) = 2. They suggest that α instead of being superuniversal might be equal to 1/d.