Showing papers by "University of Geneva published in 1992"

The pathophysiology of tumor necrosis factors.

Abstract: Tumor necrosis factor (TNF) came to birth in a strange way. It made its entry into the world of biology and medicine when Lloyd Old discovered that the capacity to induce, in vivo and in vitro, the necrosis of some mouse tumors could be ascribed to a factor (rapidly identified as a protein) present in the blood after LPS injection ( 1 ) . Then, at what may appear as an unsurmountable biological distance but what geographically was a very close event (occurring in New York City virtually on the other side of the street), Anthony Cerami discovered that the intriguing state of cachexia associated with hypertriglyceridemia presented by rabbits chronically infected with Trypanosomia brucei results from the presence of a serum protein which he called "cachectin." Purification of cachectin by A. Cerami and B. Beutler led them to realize that it is also an essential mediator in the state of shock induced by LPS injection in mice and is the same molecule as TNF (2, 3). It required little time for these three parents to recognize that their common child, with its so disparate talents, was unusually gifted. What they could not foresee was that, within a very few years, TNF would turn out to be a child prodigy, eliciting, because of its diverse effects, the publication of several papers per day. Somewhat ironically, it appears now that TNF rarely induces in vivo direct cytolysis of natural tumors (it can even be made by them), that it may not play a significant role in the cachexia most commonly observed in humans, that resulting from cancer, and that the critical role of TNF in shock is shared by other mediators, particularly interleukin 1 (ILl ), its frequent com-

Establishment of 2-mercaptoethanol-dependent differentiated insulin-secreting cell lines.

Abstract: New insulin-secreting cell lines (INS-1 and INS-2) were established from cells isolated from an x-ray-induced rat transplantable insulinoma. The continuous growth of these cells was found to be dependent on the reducing agent 2-mercaptoethanol. Removal of this thiol compound caused a 15-fold drop in total cellular glutathione levels. These cells proliferated slowly (population doubling time about 100 h) and, in general, showed morphological characteristics typical of native beta-cells. Most cells stained positive for insulin and did not react with antibodies against the other islet hormones. The content of immunoreactive insulin was about 8 micrograms/10(6) cells, corresponding to 20% of the native beta-cell content. These cells synthesized both proinsulin I and II and displayed conversion rates of the two precursor hormones similar to those observed in rat islets. However, glucose failed to stimulate the rate of proinsulin biosynthesis. In static incubations, glucose stimulated insulin secretion from floating cell clusters or from attached cells. Under perifusion conditions, 10 mM but not 1 mM glucose enhanced secretion 2.2-fold. In the presence of forskolin and 3-isobutyl-1-methylxanthine, increase of glucose concentration from 2.8-20 mM caused a 4-fold enhancement of the rate of secretion. Glucose also depolarized INS-1 cells and raised the concentration of cytosolic Ca2+. This suggests that glucose is still capable of eliciting part of the ionic events at the plasma membrane, which leads to insulin secretion. The structural and functional characteristics of INS-1 cells remained unchanged over a period of 2 yr (about 80 passages). Although INS-2 cells have not been fully characterized, their insulin content was similar to that of INS-1 cells and they also remain partially sensitive to glucose as a secretagogue. INS-1 cells retain beta-cell surface antigens, as revealed by reactivity with the antigangloside monoclonal antibodies R2D6 and A2B5. These findings indicate that INS-1 cells have remained stable and retain a high degree of differentiation which should make them a suitable model for studying various aspects of beta-cell function.

Molecular dissection of the secretory pathway

Abstract: A combination of biochemistry in animal cell-free systems and genetics in yeast is revealing the molecular machinery of the secretory pathway of eukaryotes. Transporting vesicles have a simple coat structure and employ a general mechanism for fusion that is conserved in evolution.

Functional and Evolutionary Relationships Among Diverse Oxygenases

Abstract: Oxygenases that incorporate one or two atoms of dioxygen into substrates are found in many metabolic pathways In this article, representative oxygenases, principally those found in bacterial pathways for the degradation of hydrocarbons, are reviewed Monooxygenases, discussed in this chapter, incorporate one hydroxyl group into substrates In this reaction, two atoms of dioxygen are reduced to one hydroxyl group and one H2O molecule by the concomitant oxidation of NAD(P)H Dioxygenases catalyze the incorporation of two atoms of dioxygen into substrates Two types of dioxygenases, aromatic-ring dioxygenases and aromatic-ring-cleavage dioxygenases, are discussed The aromatic-ring dioxygenases incorporate two hydroxyl groups into aromatic substrates, and cis-diols are formed This reaction also requires NAD(P)H as an electron donor Aromatic-ring-cleavage dioxygenases incorporate two atoms of dioxygen into aromatic substrates, and the aromatic ring is cleaved This reaction does not require an external reductant All the oxygenases possess a cofactor, a transition metal, flavin or pteridine, that interacts with dioxygen The concerted reactions between dioxygen and carbon in organic compounds are spin forbidden The cofactor is used to overcome this restriction For the oxygenases that require the NAD(P)H cofactor, the enzyme reaction is separated into two steps, the oxidation of NAD(P)H to generate two reducing equivalents, and the hydroxylation of substrates Flavoprotein hydroxylases that catalyze the monohydroxylation of the aromatic ring carry out these two reactions on a single polypeptide chain In other oxygenases, the NAD(P)H oxidation and a hydroxylation reaction are catalyzed by two separate polypeptides that are linked by a short electron-transport chain Two reducing equivalents generated by the oxidation of NAD(P)H are transferred through the electron-transport chain to the cofactor on a hydroxylase component that they reduce Dioxygen couples with the reduced cofactor and subsequently hydroxylates substrates The electron-transport chains associated with oxygenases contain at least two redox centers The first redox center is usually a flavin, while the second is an iron-sulfur cluster The electron transport is initiated by a single two-electron transfer from NAD(P)H to a flavin, followed by two single-electron transfers from the flavin to an iron-sulfur cluster The primary sequences of many oxygenases have been determined, and according to their sequence similarities, the oxygenases can be grouped into several protein families Among proteins of the same family, the sequences in regions involved in cofactor binding are strongly conserved Local sequence similarities are also observed among oxygenases from different families, primarily in regions involved in cofactor binding

New social movements and political opportunities in Western Europe

Abstract: We present a number of concepts and hypotheses concerning the impact of the political opportunity structure on the mobilisation pattern of new social movements in Western Europe The hypotheses refer to the general level of mobilisation in a given country, the general forms and strategies of action employed, the system level at which mobilisation is typically oriented and the development of the level of mobilisation across time The hypotheses are tested in a comparative analysis of France, Germany, the Netherlands and Switzerland The analysis reveals country-specific variations in the mobilisation patterns of new social movements, which are largely in line with the theoretical expectations and serve to confirm the relevance of the political process approach for the study of social movements

Subhypnotic doses of propofol possess direct antiemetic properties.

Abstract: Propofol is associated with a low incidence of postoperative nausea and vomiting. In a prospective, randomized, double-blind, placebo-controlled study, we investigated the possible direct antiemetic properties of a subhypnotic dose of propofol. Fifty-two ASA physical status I or II patients, aged 15

Simulation of Facial Muscle Actions Based on Rational Free Form Deformations

Abstract: This paper describes interactive facilities for simulating abstract muscle actions using rational free form deformations (RFFD). The particular muscle action is simulated as the displacement of the control points of the control-unit for an RFFD defined on a region of interest. One or several simulated muscle actions constitute a minimum perceptible action (MPA), which is defined as the atomic action unit, similar to action unit (AU) of the facial action coding system (FACS), to build an expression

Position effect variegation and chromatin proteins.

Abstract: Variegated phenotypes often result from chromosomal rearrangements that place euchromatic genes next to heterochromatin In such rearrangements, the condensed structure of heterochromatin can spread into euchromatic regions, which then assume the morphology of heterochromatin and become transcriptionally inactive In position-effect variegation (PEV) therefore, gene inactivation results from a change in chromatin structure PEV has been intensively investigated in the fruitfly Drosophila, where the phenomenon allows a genetic dissection of chromatin components Consequently, many genes have been identified which, when mutated, act as dominant modifiers (suppressors or enhancers) of PEV Data available already demonstrate that genetic, molecular and developmental analysis of these genes provides an avenue to the identification of regulatory and structural chromatin components, and hence to fundamental aspects of chromosome structure and function

Dressing animated synthetic actors with complex deformable clothes

Abstract: Discusses the use of physics-based models for animating clothes on synthetic actors in motion. In this approach, cloth pieces are first designed with polygonal panels in two dimensions, and are then seamed and attached to the actor's body in three dimensions. After the clothes are created, physical properties are simulated and then clothes are animated according to the actor's motion in a physical environment. The paper describes the physical models used and then addresses several problems encountered. It examines how to constrain the elements of deformable objects which are either seamed together or attached to rigid moving objects. It also describes a new approach to the problem of handling collisions among the cloth elements themselves, or between a cloth element and a rigid object like the human body. Finally, the paper discusses how to reduce the number of parameters for improving the interface between the animator and the physics-based model

Categorical versus coordinate spatial relations: computational analyses and computer simulations

Abstract: Results of 4 sets of neural network simulations support the distinction between categorical and coordinate spatial relations representations: (a) Networks that were split so that different hidden units contributed to each type of judgment performed better than unsplit networks; the reverse was observed when they made 2 coordinate judgments. (b) Both computations were more difficult when finer discriminations were required; this result mirrored findings with human Ss. (c) Networks with large, overlapping "receptive fields" performed the coordinate task better than did networks with small, less overlapping receptive fields, but vice versa for the categorical task; this suggests a possible basis for observed cerebral lateralization of the 2 kinds of processing. (d) The previously observed effect of stimulus contrast on this hemispheric asymmetry could reflect contributions of more neuronal input in high-contrast conditions.

Evolution of collagen arthritis in mice is arrested by treatment with anti-tumour necrosis factor (TNF) antibody or a recombinant soluble TNF receptor.

Abstract: Immunization of DBA/1 mice with type II collagen within complete Freund's adjuvant leads to arthritis, lasting more than 3 months. Injection of anti-tumour necrosis factor (TNF) IgG, 2 and 3 weeks after immunization prevented the development of arthritis in the following months. This treatment had no effect when started 2 months after induction of the disease. A soluble form of the human recombinant TNF receptor type-beta (rsTNFR-beta), continuously infused at a rate of 20 micrograms/day during the second and third week after immunization, also had a long-term protective effect. Anti-TNF antibody had no effect upon the production of anti-type II collagen antibodies. These results indicate that TNF is critically involved in an early phase of this arthritis.

Cathinone, a Natural Amphetamine

Abstract: Cathinone is an alkaloid that has been discovered some fifteen years ago in the leaves of the khat bush. This plant grows in East Africa and in southern Arabia, and the inhabitants of these regions frequently chew khat because of its stimulating properties. Cathinone, which is S(–)-α-aminopropiophenone, was soon found to have a pharmacological profile closely resembling that of amphetamine; indeed, in a wide variety of in vitro and in vivo experiments it was demonstrated that cathinone shares the action of amphetamine on CNS as well as its sympathomimetic effects; thus, for example, drug-conditioned animals will not distinguish between cathinone and amphetamine. These various observations were confirmed by a clinical experiment showing that cathinone also in humans produces amphetamine-like objective and subjective effects. Finally, it was demonstrated that cathinone operates through the same mechanism as amphetamine, i.e. it acts by releasing catecholamines from presynaptic storage sites. Thus, much experimental evidence indicates that cathinone is the main psychoactive constituent of the khat leaf and that, in fact, this alkaloid is a natural amphetamine.

specificity of Escherichia coli endoribonuclease RNase E: in vivo and in vitro analysis of mutants in a bacteriophage T4 mRNA processing site

Abstract: Endoribonuclease RNase £ has an important role in the processing and degradation of bacteriophage T4 and Escherichia coli mRNAs. We have undertaken a mutational analysis of the -71 RNase E processing site of T4 gene 32. A Series of mutations were introduced into a synthetic T4 sequence cloned on a plasmid, and their effects on processing were analyzed in vivo. The same mutations were transferred into T4 by homologous recombination. In both the plasmid and the phage contexts the processing of the transcripts was similarly affected by the mutations. Partially purified RNase E has also been used to ascertain the effect of these mutations on RNase E processing in vitro. The hierarchy of the efficiency of processing of the various mutant transcripts was the same in vivo and in vitro. These results and an analysis of all of the known putative RNase E sites suggest a consensus sequence RAUUW (R = A or G; W ^ A or U) at the cleavage site. Modifications of the stem-loop structure downstream of the -71 site indicate that a secondary structure is required for RNase E processing. Processing by RNase E was apparently inhibited by sequences that sequester the site in secondary structure.

Broad-host-range Rhizobium species strain NGR234 secretes a family of carbamoylated, and fucosylated, nodulation signals that are O-acetylated or sulphated

Abstract: Rhizobium species strain NGR234 is the most promiscuous known rhizobium. In addition to the non-legume Parasponia andersonii, it nodulates at least 70 genera of legumes. Here we show that the nodulation genes of this bacterium determine the production of a large family of Nod-factors which are N-acylated chitin pentamers carrying a variety of substituents. The terminal non-reducing glucosamine is N-acylated with vaccenic or palmitic acids, is N-methylated, and carries varying numbers of carbamoyl groups. The reducing N-acetyl-glucosamine residue is substituted on position 6 with 2-O-methyl-L-fucose which may be acetylated or sulphated or non-substituted. All three internal residues are N-acetylated. At pico- to nanomolar concentrations, these signal molecules exhibit biological activities on the tropical legumes Macroptilium and Vigna (Phaseoleae), as well as on both the temperate genera Medicago (Trifoliae) and Vicia (Viciae). These data strongly suggest that the uniquely broad host range of NGR234 is mediated by the synthesis of a family of varied sulphated and non-sulphated lipo-oligosaccharide signals.

Differential distribution of neurofibrillary tangles in the cerebral cortex of dementia pugilistica and Alzheimer's disease cases.

Abstract: Head trauma has been associated with the occurrence of Alzhiemer's disease and plays a clear role in the etiopathogenesis of the boxers encephalopathy referred to as dementia pugilistica. Neurofibrillary tangles (NFT), one of the pathological hallmarks of Alzheimer's disease are observed in very high densities in the brains of former professional boxers suffering from dementia pugilistica. In Alzheimer's disease, NFT display striking regional and laminar distribution patterns that have been correlated with the localization of neurons forming specific corticocortical connections. In dementia pugilistica cases, NFT were concentrated in the superficial layers in the neocortex, whereas in Alzheimer's disease they predominated in the deep layers. Thus, the association cortex of brains from dementia pugilistica patients demonstrated an inverse NFT distribution as compared to Alzheimer's disease. This finding suggests that a more circumscribed population of cortical pyramidal neurons might be affected in dementia pugilistica than in Alzheimer's disease.

Decomposition and nondifferentiable optimization with the projective algorithm

Abstract: This paper deals with an application of a variant of Karmarkar's projective algorithm for linear programming to the solution of a generic nondifferentiable minimization problem. This problem is closely related to the Dantzig-Wolfe decomposition technique used in large-scale convex programming. The proposed method is based on a column generation technique defining a sequence of primal linear programming maximization problems. Associated with each problem one defines a weighted potential function which is minimized using a variant of the projective algorithm. When a point close to the minimum of the potential function is reached, a corresponding point in the dual space is constructed, which is close to the analytic center of a polytope containing the solution set of the nondifferentiable optimization problem. An admissible cut of the polytope, corresponding to a new supporting hyperplane of the epigraph of the function to minimize, is then generated at this approximate analytic center. In the primal space this new cut translates into a new column for the associated linear programming problem. The algorithm has performed well on a set of convex nondifferentiable programming problems.

SEC21 is a gene required for ER to Golgi protein transport that encodes a subunit of a yeast coatomer

Abstract: NON-CLATHRIN coated vesicles have been implicated in early steps of intercompartmental transport1–4. A distinct set of coat proteins are peripherally associated with the exterior of purified mammalian intra-Golgi transport vesicles5. The 'coatomer', a cytosolic complex containing a similar subunit composition to and sharing at least one subunit (β-COP) with the coat found on vesicles, has been postulated to be the precursor of this non-clathrin coat6. Here we describe the characterization of SEC21, an essential gene required for protein transport from the endoplasmic reticulum to the Golgi in the yeast Saccharomyces cerevisiae. The 105K product of this gene, Sec21p, participates in a cytosolic complex that we show to be a yeast homologue of the mammalian coatomer. These observations demonstrate that a non-clathrin coat protein plays an essential role in intercompartmental transport.

Catalytic asymmetric synthesis of Secondary (E)-allyl alcohols from acetylenes and aldehydes via (1-alkenyl)zinc intermediates. Preliminary Communication

Abstract: Hydroboration of aliphatic 1-alkynes with freshly prepared dicyclohexylborane (1 mol-equiv., hexane), treatment of the resulting [(E)-1-alkenyl]boranes 5 with Et2Zn or Me2Zn (1.05 mol-equiv.) followed by addition of (−)-3-exo-(dimethylamino)isoborneol (DAIB, 8; 0.01 mol-equiv.), subsequent addition of a solution of an aromatic or aliphatic aldehyde (1 mol-equiv., hexane), and quenching with aq. NH4Cl provided (E)-allyl alcohols 6 usually in 70–95% yield with 79–98% enantiomeric excess (Scheme 3 and Table).