Basics of the virology of HIV-1 and its replication.

Human immunodeficiency virus is undoubtedly the causative agent of AIDS. The understanding of HIV-1 pathogenesis is essential to develop and maintain antiretroviral treatment and vaccination. Since the first isolation of HIV-1 in cell culture, thousands of publications dealing with HIV and/or AIDS per year were released. In this review we give a basic overview of the virology of HIV-1 including the functions of the different HIV-1 proteins required for effective viral replication. Moreover, we summarize the interactive processes between HIV-1 and its target cells. Finally, the HIV-1 specific immune response and the current status of antiretroviral therapy are briefly described in this review.     

Multidimensional Chromatographic and Hyphenated Techniques for Hydrophilic Copolymers, 1

Summary: The chromatographic analysis of hydrophilic copolymers is complicated due to the fact that in most cases aqueous eluents must be used. In aqueous eluents different polar and ionic effects may disturb the selective interactions between the macromolecules and the stationary phase making it impossible to separate such copolymers with regard to chemical composition. Therefore, 2D chromatography combining a separation according to composition with a separation according to molar mass has been applied mostly to polymers that are soluble in organic solvents. The present contribution describes experimental approaches to analyze such hydrophilic copolymers by 2D‐chromatography. For a model polymer system resulting from the copolymerization of methacrylic acid and a poly(ethylene glycol) macromonomer, it is shown that different analytical techniques including SEC, LC‐CC, MALDI‐TOF MS and 2D chromatography can be used to analyze the different parameters of molecular heterogeneity of such copolymers.

2D separation of poly(MPEG‐MM 2), 1^st dimension: LC‐CC, 2^nd dimension: SEC.     

Systematic isolation of transducing phages for Myxococcus xanthus.

Six new phages active on Myxococcus xanthus have been isolated from cultures of myxobacteria. The six are all capable of transduction, and they fall into three groups. Members of one group have long contractile tails, have a characteristic neutralization antigen, and resemble the previously described M×4. Members of a second group, exemplified by M×8, have very short tails and a characteristic antigen. M×9, the sole member of the third group, has a very short tail and a characteristic antigen. Phage M×8, which is active on fruiting as well as nonfruiting strains of M. xanthus, can transduce auxotrophic, antibiotic resistance and motility markers in M. xanthus. Although crude lysates of M×8 contain 58-nm diameter particles with a tail and 29-nm particles without tail, only 58-nm particles can form plaques and transduce. The plaque-forming particles of M×8 possess a single DNA molecule of 56,000 base pairs with a buoyant density of 1.726 g/cm³, virtually identical to that of the DNA from its host.     

Phase Variation of Campylobacter jejuni 81-176 Lipooligosaccharide Affects Ganglioside Mimicry and Invasiveness In Vitro

The outer cores of the lipooligosaccharides (LOS) of many strains of Campylobacter jejuni mimic human gangliosides in structure. A population of cells of C. jejuni strain 81-176 produced a mixture of LOS cores which consisted primarily of structures mimicking GM(2) and GM(3) gangliosides, with minor amounts of structures mimicking GD(1b) and GD(2). Genetic analyses of genes involved in the biosynthesis of the outer core of C. jejuni 81-176 revealed the presence of a homopolymeric tract of G residues within a gene encoding CgtA, an N-acetylgalactosaminyltransferase. Variation in the number of G residues within cgtA affected the length of the open reading frame, and these changes in cgtA corresponded to a change in LOS structure from GM(2) to GM(3) ganglioside mimicry. Site-specific mutation of cgtA in 81-176 resulted in a major LOS core structure that lacked GalNAc and resembled GM(3) ganglioside. Compared to wild-type 81-176, the cgtA mutant showed a significant increase in invasion of INT407 cells. In comparison, a site-specific mutation of the neuC1 gene resulted in the loss of sialic acid in the LOS core and reduced resistance to normal human serum but had no affect on invasion of INT407 cells.     

Inhibition by monensin of human cytomegalovirus DNA replication

Summary Monensin, at concentrations which depended on the multiplicity of infection, was found to prevent DNA replication of human cytomegalovirus (HCMV) as well as production of viral progeny in human foreskin fibroblasts. The drug did not affect DNA replication of herpes simplex virus. Inhibition of consecutive HCMV DNA synthesis was also observed following delayed addition of the drug within 12–24 hours postinfection, but was fully reversible upon its removal. Viral replication proceeded, however, without impairment in cultures treated with monensin prior to infection. Induction of viral DNA polymerase activity was not impeded by the inhibitor. Analysis of protein- and glycoprotein synthesis revealed that monensin interfered with the production of a number of HCMV-specific polypeptides. Furthermore, evidence was obtained that the drug may hinder intracellular transport of a 135 kd glycopolypeptide.With 6 Figures     

Phosphatidylglycerolphosphate synthase encoded by the PEL1/PGS1 gene in Saccharomyces cerevisiae is localized in mitochondria and its expression is regulated by phospholipid precursors

The PEL1/PGS1 gene of the yeast Saccharomyces cerevisiae is essential for the viability of rho ^–/rho° mutants and the normal cardiolipin content of cells. The PEL1-GFP fusion gene has been found to complement the pel1/pgs1 mutation and its fluorescent protein was localized to mitochondria similarly to the β-galactosidase activity of a protein encoded by the PEL1-lacZ fusion gene. The expression of the PEL1-lacZ reporter gene was repressed in cells grown in the presence of inositol and choline, reduced in the ino2 and ino4 strains, but constitutive in the opi1 null-mutant strain. The results demonstrate that Pel1p, playing a vital role in cells impaired in the mitochondrial DNA, is localized in the mitochondria and expressed in response to inositol and choline. Received: 15 June / 15 July 1998     

Cation channels,cell volume and the death of an erythrocyte

Similar to a variety of nucleated cells, human erythrocytes activate a non-selective cation channel upon osmotic cell shrinkage. Further stimuli of channel activation include oxidative stress, energy depletion and extracellular removal of Cl^–. The channel is permeable to Ca²⁺ and opening of the channel increases cytosolic [Ca²⁺]. Intriguing evidence points to a role of this channel in the elimination of erythrocytes by apoptosis. Ca²⁺ entering through the cation channel stimulates a scramblase, leading to breakdown of cell membrane phosphatidylserine asymmetry, and stimulates Ca²⁺-sensitive K⁺ channels, thus leading to KCl loss and (further) cell shrinkage. The breakdown of phosphatidylserine asymmetry is evidenced by annexin binding, a typical feature of apoptotic cells. The effects of osmotic shock, oxidative stress and energy depletion on annexin binding are mimicked by the Ca²⁺ ionophore ionomycin (1 µM) and blunted in the nominal absence of extracellular Ca²⁺. Nevertheless, the residual annexin binding points to additional mechanisms involved in the triggering of the scramblase. The exposure of phosphatidylserine at the extracellular face of the cell membrane stimulates phagocytes to engulf the apoptotic erythrocytes. Thus, sustained activation of the cation channels eventually leads to clearance of affected erythrocytes from peripheral blood. Susceptibility to annexin binding is enhanced in several genetic disorders affecting erythrocyte function, such as thalassaemia, sickle-cell disease and glucose-6-phosphate dehydrogenase deficiency. The enhanced vulnerability presumably contributes to the shortened life span of the affected erythrocytes. Beyond their role in the limitation of erythrocyte survival, cation channels may contribute to the triggering of apoptosis in nucleated cells exposed to osmotic shock and/or oxidative stress.     

The impact of the Women's Health Initiative Randomized Controlled Trial 2002 on perceived risk communication and use of postmenopausal hormone therapy in Germany

OBJECTIVE: The purpose of this representative, nationwide telephone survey was to collect information about postmenopausal hormone therapy (HT) use in relation to women's knowledge about the Women's Health Initiative Randomized Controlled Trial 2002 (WHI-RCT) in Germany. DESIGN: During July 2003, telephone interviews were conducted with randomly selected women aged 45 to 60 years (N = 10,030; response 59.9%; completed interviews n = 6,007). They were asked about information sources regarding the WHI-RCT, and use of HT in conjunction with it. RESULTS: Most women stated that they knew about the WHI-RCT (88.6%), and those with high educational status appeared to have more information than those with middle or low educational status. Among informed women (uninformed excluded), 46.6% continued, 25.7% stopped, and 14.2% ceased use of HT before the WHI-RCT. The prevalence of lifetime use of HT was higher in West Germany (37.4%) than in East Germany (29.2%), the highest prevalence of use was in the group aged 55 to 59 years. The most common reason to continue HT was the benefit risk assessment by physicians (58%); the most common reason to stop HT were women's perceptions that the risks of HT exceeded the benefits (56%). If information was solely given by physicians, women were more likely to continue HT (60.4%), compared with mass media (46.1%), as a source of information. CONCLUSIONS: The survey demonstrates the impact of the WHI-RCT in Germany, and shows that both the media and advice given by physicians were important. Women who continued to use HT did so largely because of their physician's advice. Women who discontinued were mainly those who had a negative subjective perception about risk of HT.     

Dopamine in the orbitofrontal cortex regulates operant responding under a progressive ratio of reinforcement in rats

Prefrontocortical dopamine (DA) plays an essential role in the regulation of cognitive functions and behavior. The orbitofrontal cortex (OFC) receives a dopaminergic projection from the ventral tegmental area and is particularly important for goal-directed appetitive behaviors and for the neural representation of reward value. We here examined the effects of DA receptor blockers locally infused into the OFC, on instrumental behavior under a progressive schedule of reinforcement. After continuous reinforcement training (lever pressing for casein pellets) rats received bilateral intra-OFC-infusions of the DA D1-receptor antagonist SCH23390 (3 μg/0.5 μl), the DA D2-receptor antagonist sulpiride (3 μg/0.5 μl), or phosphate buffered saline through chronically indwelling cannulae. Immediately after infusion they were tested under a time-constrained progressive ratio schedule of reinforcement (3, 6, 9, 12, … lever presses for 1 casein pellet within 180 s). Both SCH23390 and sulpiride led to a significant reduction of the break point (cessation to respond to the increasing criterion of instrumental effort) compared to vehicle infusions. A food preference test revealed no drug effects on the amount of consumed pellets and on the preference of casein pellets over laboratory chow. Leftward shifts of the break point in progressive ratio tasks indicate a disturbance of the mechanisms that translate motivation into appetitive behavior under conditions of increasing instrumental effort. Therefore, our data indicate that orbitofrontal dopamine is necessary for reward-related instrumental behavior.