Inter-retroviral fusion mediated by human immunodeficiency virus or murine leukemia virus glycoproteins: independence of cellular membranes and membrane vesicles.

We have recently demonstrated for the first time that inter-retroviral membrane fusion, i.e., membrane fusion between individual retroviral particle populations with incorporated HIV-1 Env and cellular receptors, respectively, can occur (Sparacio et al.

[Aortoiliac reconstruction after kidney transplantation. Strategies to avoid ischemic damage of the transplant].

Introduction: The rising life expectancy of patients undergoing kidney transplantation and the improvement in the function rate of the allografts have led to an increasing number of patients suffering from arteriosclerosis-related diseases of the aortoiliac arteries. In these particular cases, an interruption of the blood supply of the allograft is always necessary for operative repair of the aortic and iliac arteries. This means a high risk of ischemic damage to the transplanted kidney.

Exploring the pathway structure of metabolism: decomposition into subnetworks and application to Mycoplasma pneumoniae.

Motivation: Reconstructing and analyzing the metabolic map of microorganisms is an important challenge in bioinformatics. Pathway analysis of large metabolic networks meets with the problem of combinatorial explosion of pathways. Therefore, appropriate algorithms for an automated decomposition of these networks into smaller subsystems are needed.

Potential contact sites between the protein and RNA subunit in the Bacillus subtilis RNase P holoenzyme.

We have detected by nucleotide analog interference mapping (NAIM) AMPalphaS and IMPalphaS modifications in Bacillus subtilis RNase P RNA that interfere with binding of the homologous protein subunit. Interference as well as some enhancement effects were clustered in two main areas, in P10.1a/L10.

Working memory limitation as a source of confusion in the abstract THOG task.

Limitations of working memory are proposed as a major determinant of problem difficulty in the THOG task. This task is a logical reasoning task which uses an exclusive disjunction and requires hypothetico-deductive reasoning. Four experiments with students of mathematics or psychology were used to test the hypotheses that, first, guiding participants' attention facilitates the task and, second, the use of paper and pencil as external problem representation reliefs working memory load.

Soybean mosaic virus (SMV) and the SMV Resistance Gene (Rsv(1)): Influence on Phomopsis spp. Seed Infection in an Aphid Free Environment.

Infection of soybean [Glycine max (L.) Merr.] plants with Soybean mosaic virus (SMV) has been reported to enhance Phomopsis spp.

Inhibition of release of lentivirus particles with incorporated human influenza virus haemagglutinin by binding to sialic acid-containing cellular receptors.

Mutants of the haemagglutinin (HA) gene of human influenza virus A/Aichi/2/68 (H3N2) encoding HA proteins that are proteolytically cleaved intracellularly, defective in binding to cellular receptors or defective for acylation within the cytoplasmic C terminus have been generated. Here, the properties of these mutated HA molecules are described and their incorporation into the lipid membrane of released human immunodeficiency virus (HIV)-like particles is analysed. It is demonstrated that, when produced from cells coexpressing any of the binding-competent Aichi-HA molecules, release of HIV-like particles into the extracellular medium is reduced and the particles that are released fail to incorporate Aichi-HA.

Exploring the minimal substrate requirements for trans-cleavage by RNase P holoenzymes from Escherichia coli and Bacillus subtilis.

We analysed the processing of small bipartite model substrates by Escherichia coli and Bacillus subtilis RNase P and corresponding hybrid enzymes. We demonstrate specific trans-cleavage of a model substrate with a 4 bp stem and a 1 nucleotide (nt) 5' flank, representing to date the smallest mimic of a natural RNase P substrate that could be processed in trans at the canonical RNase P cleavage site. Processing efficiencies decreased up to 5000-fold when the 5' flank was shortened from 3 to 1 nt.

Generation of a flexible cell line with regulatable, high-level expression of HIV Gag/Pol particles capable of packaging HIV-derived vectors.

HIV-derived vectors are of potential clinical relevance due to their ability to transduce nondividing cells in vitro and in vivo. However, the generation of cell lines stably and reproducibly expressing high amounts of defined subviral particles, capable of packaging and transducing HIV-derived vectors, has been hampered by the cytotoxicity of some of the required gene products, in particular of the HIV-1 protease. The successful use of regulatable gene expression systems to overcome this problem requires that the remaining basally expressed gene product activity is below the threshold for cytotoxicity.

Cooperation and competition in the evolution of ATP-producing pathways.

Heterotrophic organisms generally face a trade-off between rate and yield of adenosine triphosphate (ATP) production. This trade-off may result in an evolutionary dilemma, because cells with a higher rate but lower yield of ATP production may gain a selective advantage when competing for shared energy resources. Using an analysis of model simulations and biochemical observations, we show that ATP production with a low rate and high yield can be viewed as a form of cooperative resource use and may evolve in spatially structured environments.

Correlation between processing efficiency for ribonuclease P minimal substrates and conformation of the nucleotide -1 at the cleavage position.

It is demonstrated that acceptor stem duplexes derived from native tRNAs which contain a three-nucleotide extension at the 5'-terminus of mature tRNA are minimal substrates for ribonuclease P from both Escherichia coli and Bacillus subtilis. Variants with a cytidine at position -1 are most efficiently processed whereas the G -1 variant represents a comparatively poor substrate. An A -1 acceptor stem variant is a slightly better substrate than the G -1 variant though generally distinctly less efficient than the C -1 duplex.

Long-term results after surgical reconstruction for renal artery fibromuscular dysplasia.

Objectives: To study the initial and long-term results of surgery for renal artery fibromuscular dysplasia (RFMD).

Patients And Methods: All patients undergoing renal artery reconstruction (RAR) performed for RFMD between January 1980 and December 1997, were studied. The preprocedural and postprocedural clinical records of 101 patients (80 women, 21 men; mean age at surgery 43 years) were retrospectively reviewed.

Epidemiology and host- and variety-dependent characteristics of infection due to Cryptococcus neoformans in Australia and New Zealand. Australasian Cryptococcal Study Group.

A prospective population-based study was conducted in Australia and New Zealand during 1994-1997 to elucidate the epidemiology of cryptococcosis due to Cryptococcus neoformans var. neoformans (CNVN) and C. neoformans var.

Healing characteristics of small-calibre vascular prostheses coated with plasmin-treated fibrin--an experimental study.

Background: The autogenous vein represents the graft material of choice in crural and pedal bypass surgery. Because of the numerous problems concerning the graft harvesting and the quality of autogenous vein material an equally good allogenous graft is urgently needed. Up to the present times no such graft material has been able to achieve the success of vein grafts.

Membrane fusion between retroviral particles: host-range extension and vaccine prospects.

We have analyzed if different populations of retroviral particles carrying the viral and cellular receptors of membrane viruses, respectively, are able to specifically fuse with each other. Using the glycoprotein of human immunodeficiency virus type 1 and its cellular receptor complex, we demonstrate that interviral membrane fusion can, indeed, occur and that the resultant fused viral structures are able to infect cells and transduce a marker gene. On the one hand, these results have relevance for the development of vaccine strategies based on fusion-induced conformational epitopes on the viral glycoprotein.

Effects of phosphorothioate modifications on precursor tRNA processing by eukaryotic RNase P enzymes.

The cleavage mechanism has been studied for nuclear RNase P from Saccharomyces cerevisiae, Homo sapiens sapiens and Dictyostelium discoideum, representing distantly related branches of the Eukarya. This was accomplished by using precursor tRNAs (ptRNAs) carrying a single Rp or Sp-phosphorothioate modification at the normal RNase P cleavage site (position -1/+1). All three eukaryotic RNase P enzymes cleaved the Sp-diastereomeric ptRNA exclusively one nucleotide upstream (position -2/-1) of the modified canonical cleavage site.

[Results of conventional surgical therapy of abdominal aortic aneurysms since the beginning of the "endovascular era"].

Introduction: In 1990 the new method of endovascular graft treatment of abdominal aortic aneurysms (AAA) emerged. For this reason we analyzed the results of open surgery for AAA in our department to consider the question of standard therapy.

Methods: In a retrospective study the medical data of 941 consecutive patients treated by open surgery in a single center from 1990 to 1997 (mean age 67 years, 14.

Export and transport of tRNA are coupled to a multi-protein complex.

Vigilin is a ubiquitous multi heterogeneous nuclear ribonucleoprotein (hnRNP) K homologous (KH)-domain protein. Here we demonstrate that purified recombinant human vigilin binds tRNA molecules with high affinity, although with limited specificity. Nuclear microinjection experiments revealed for the first time that the immuno-affinity-purified nuclear vigilin core complex (VCC(N)) as well as recombinant vigilin accelerate tRNA export from the nucleus in human cells.

Incorporation of wild-type and C-terminally truncated human epidermal growth factor receptor into human immunodeficiency virus-like particles: insight into the processes governing glycoprotein incorporation into retroviral particles.

Previous results have indicated that incorporation of surface glycoprotein into retroviral particles is not a specific process and that many heterologous viral and cellular glycoproteins can be incorporated as long as they do not have long cytoplasmic C-terminal regions which were presumed to be sterically inhibitory. In this study, this concept has been directly examined by analyzing the incorporation of the wild-type human epidermal growth factor receptor (Wt-EGFR) and of a C-terminally truncated mutant of Wt-EGFR (Tr-EGFR) into human immunodeficiency virus (HIV)-like particles. Incorporation was directly analyzed at the protein level and by immunogold labelling of enriched HIV-like particles.

METATOOL: for studying metabolic networks.

Motivation: To reconstruct metabolic pathways from biochemical and/or genome sequence data, the stoichiometric and thermodynamic feasibility of the pathways has to be tested. This is achieved by characterizing the admissible region of flux distributions in steady state. This region is spanned by what can be called a convex basis.

Guanosine 2-NH2 groups of Escherichia coli RNase P RNA involved in intramolecular tertiary contacts and direct interactions with tRNA.

We have identified by nucleotide analog interference mapping (NAIM) exocyclic NH2 groups of guanosines in RNase P RNA from Escherichia coli that are important for tRNA binding. The majority of affected guanosines represent phylogenetically conserved nucleotides. Several sites of interference could be assigned to direct contacts with the tRNA moiety, whereas others were interpreted as reflecting indirect effects on tRNA binding due to the disruption of tertiary contacts within the catalytic RNA.

Open surgery or endovascular treatment of the abdominal aortic aneurysm--quality assurance is urgently needed.

Purpose: The endovascular treatment of the abdominal aortic aneurysm (AAA) seemed to promise great advantages over the open surgery. The current results do not show an improvement compared to the conventional therapy. New kinds of complications have appeared.

tRNA is entrapped in similar, but distinct, nuclear and cytoplasmic ribonucleoprotein complexes, both of which contain vigilin and elongation factor 1 alpha.

Vigilin, which is found predominantly in cells and tissues with high levels of protein biosynthesis, was isolated in its native form from human HEp-2 cells (A.T.C.

Cryptococcus neoformans var. gattii infection in northern Australia: existence of an environmental source other than known host eucalypts.

The 2 known host trees of Cryptococcus neoformans var. gattii, Eucalyptus camaldulensis and E. tereticornis, do not occur naturally in the 'Top End' of the Northern Territory (NT) of Australia.