Structural determinants of the rate of protein folding

To understand the mechanism of protein folding and to assist rational design of fast-folding, non-aggregating and stable artificial enzymes, it is essential to determine the structural parameters which govern the rate constants of folding, kf. It has been found that -logkf is a linear function of the so-called chain topology parameter (CTP) within the range of 10(-1)s(-1)< or = kf < or =10(8)s(-1). The correlation between -logkf and CTP is much improved than using previously published contact order (CO) method. It has been further suggested that short sequence separations may be preferred for the establishment of stable interactions for the design of novel artificial enzymes and the modification of slow-folding proteins with aggregating intermediates.     

Does the intrinsic instability of aneuploid genomes have a causal role in cancer?

The role of aneuploidy in carcinogenesis has long been debated. We argue here that aneuploid genomes are naturally more susceptible to the types of chromosome rearrangement and epigenetic aberration that are found typically in tumor cells. In some cases, the formation of an aneuploid genome might be the initiating step in neoplastic conversion.     

Mechanisms underlying excitatory effects of group I metabotropic glutamate receptors via inhibition of 2P domain K+ channels

Group I metabotropic glutamate receptors (mGluRs) are implicated in diverse processes such as learning, memory, epilepsy, pain and neuronal death. By inhibiting background K(+) channels, group I mGluRs mediate slow and long-lasting excitation. The main neuronal representatives of this K(+) channel family (K(2P) or KCNK) are TASK and TREK. Here, we show that in cerebellar granule cells and in heterologous expression systems, activation of group I mGluRs inhibits TASK and TREK channels. D-myo-inositol-1,4,5-triphosphate and phosphatidyl-4,5-inositol-biphosphate depletion are involved in TASK channel inhibition, whereas diacylglycerols and phosphatidic acids directly inhibit TREK channels. Mechanisms described here with group I mGluRs will also probably stand for many other receptors of hormones and neurotransmitters.     

Neuronal background two-P-domain potassium channels: molecular and functional aspects

Background K+ conductances are a major determinant of membrane resting potential and input resistance, two key components of neuronal excitability. Background channels have been cloned and form a K+ channel family structurally different from Kv, KCa and Kir channels. These channels with 2P domains (K2P channels) are voltage- and time-independent. They are relatively insensitive to classical potassium channels blockers such as TEA, 4-AP, Ba2+ and Cs+. TASK and TREK subunits are widely expressed in the nervous system. Open at rest, these channels mainly contribute to the resting potential of somatic motoneurons, brainstem respiratory and chemoreceptor neurones, and cerebellar granule cells. K2P channels are regulated by numerous physical and chemical stimuli including extracellular and intracellular pH, temperature, hypoxia, pressure, bioactive lipids, and neurotransmitters. The regulation of these background K+ channels profoundly alters the neuronal excitability. For example, in Aplysia, regulation of a background potassium conductance by neurotransmitters is involved in synaptic modulation, a simple and primitive form of learning. The recent discovery that clinical compounds such as volatile anaesthetics and other neuroprotective agents including riluzole and unsaturated fatty acids activate K2P channels suggest that neuronal background K+ channels are attractive targets for the development of new drugs.     

Isomer-specific contractile effects of a series of synthetic f2-isoprostanes on retinal and cerebral microvasculature

F2-isoprostanes (F2-IsoP's) are biologically active prostanoids formed by free radical-mediated peroxidation of arachidonic acid. Four different F2-IsoP regioisomers (5-, 8-, 12-, and 15-series), each comprising eight racemic diastereomers, total 64 compounds. Information regarding the biological activity of IsoP's is largely limited to 15-F2t-IsoP (8-iso-PGF2alpha). We recently demonstrated that 15-F2t-IsoP and its metabolite, 2,3-dinor-5,6-dihydro-15-F2t-IsoP, evoked vasoconstriction and TXA2 generation in retina and brain microvasculature. We have now examined and compared the biological activities of a series of recently synthesized new 5-, 12-, and 15-series F2-IsoP isomers in pig retinal and brain microvasculature. We hereby show that other 15-series F2-IsoP isomers, 15-epi-15-F2t-IsoP, ent-15-F2t-IsoP, and ent-15-epi-15-F2t-IsoP, are also potent vasoconstrictors. The 12-series isomers tested, 12-F2t-IsoP and 12-epi-12-F2t-IsoP, also caused marked vasoconstriction. Of the 5-series isomers tested, 5-F2t-IsoP and 5-epi-5-F2t-IsoP possessed no vasomotor properties, whereas ent-5-F2t-IsoP caused modest vasoconstriction. The vasoconstriction of ent-5-F2t-IsoP, 12-F2t-IsoP, and 12-epi-12-F2t-IsoP was abolished by removal of the endothelium, by TXA2 synthase and receptor inhibitor (CGS12970, L670,596), and by receptor-mediated Ca2+ channel blockade (SK & F96365); correspondingly, these isomers increased TXB2 formation by activating Ca2+ influx (detected with fura 2-AM) through non-voltage-dependent receptor-mediated Ca2+ entry (SK & F96365 sensitive) in endothelial cells. In conclusion, as seen with 15-F2t-IsoP, ent-5-F2t-IsoP, 12-F2t-IsoP, and 12-epi-12-F2t-IsoP constricted both retinal and brain microvessels by inducing endothelium-dependent TXA2 synthesis. These new findings broaden the scope of our understanding regarding the potential involvement of F2-IsoP's as mediators of oxidant injury.     

Relative influence of bioturbation and predation on organic matter processing in river sediments: a microcosm experiment

1. Our objective was to measure the effects of bioturbation and predation on the physical characteristics and biogeochemical processes in river sediments. 2. We investigated the impacts of tubificid worms tested separately and together with an omnivore (Gammarus pulex), which does feed on tubificids, on sediment distribution, water flux, sediment organic carbon, biofilm biomass and microbial activities, and the concentrations of dissolved oxygen, dissolved organic carbon, PO, NO, NO and NH in slow filtration sand–gravel columns. We hypothesised that gammarids, which exploit the top 2–3 cm of the sediment, would modify the impact of worms at the sediment surface. 3. In experiments both with and without gammarids, bioturbation by the tubificids modified both the distribution of surface particles in the sediment column and water flux. In addition, microbial aerobic (oxygen consumption) and anaerobic (denitrification and fermentative decomposition of organic matter) processes in the sediment were stimulated in the presence of tubificid worms. However, G. pulex did not affect either the density or bioturbation activity of the tubificid worms. 4. Bioturbation by the benthos can be a major process in river habitats, contributing to the retention of organic matter in sediment dynamics. The presence of at least one predator had no effect on bioturbation in sediments. In such systems, physical heterogeneity may be sufficient for tubificids to escape from generalist predators, though more specialised ones might have more effect.     

Replication of the endosymbiotic bacterium Blochmannia floridanus is correlated with the developmental and reproductive stages of its ant host

The dynamics of replication of the intracellular endosymbiotic bacterium Blochmannia floridanus was determined during the larval development of its host ant Camponotus floridanus by real-time quantitative PCR. The bacteria were found to proliferate during pupation and immediately after the eclosion of the imagines (adult ants). In older workers the number of bacteria present in the midgut bacteriocytes decreased significantly. In contrast, the bacterial population in the ovaries was dependent on the reproductive state of the animal. An age-dependent degeneration of the midgut bacteriocytes was also investigated by microscopic techniques in males and female castes of the closely related ant species C. herculeanus and C. sericeiventris, respectively, with similar results and supports the concept of age-dependent degeneration of the midgut bacteriocytes in all castes.     

Online tool for analysis of denaturing gradient gel electrophoresis profiles

We present an online tool (EquiBands, http://www.univie.ac.at/IECB/limno/equibands/EquiBands.html) that quantifies the matching of two bands considered to be the same in different samples, even when samples are applied to different denaturing gradient gel electrophoresis gels. With an environmental example we demonstrate the procedure for the classification of two bands of different samples with the help of EquiBands.     

Helper-dependent adenoviral vector-mediated delivery of woodchuck-specific genes for alpha interferon (IFN-alpha) and IFN-gamma: IFN-alpha but not IFN-gamma reduces woodchuck hepatitis virus replication in chronic infection in vivo

Alpha interferon (IFN-alpha) and IFN-gamma are able to suppress hepadnavirus replication. The intrahepatic expression of high levels of IFN may enhance the antiviral activity. We investigated the effects of woodchuck-specific IFN-alpha (wIFN-alpha) and IFN-gamma(wIFN-gamma) on woodchuck hepatitis virus (WHV) replication in vivo by helper-dependent adenoviral (HD-Ad) vector-mediated gene transfer. The expression of biologically active IFNs was demonstrated in vitro after transduction of woodchuck cells with HD-Ad vectors encoding wIFN-alpha (HD-AdwIFN-alpha) or wIFN-gamma (HD-AdwIFN-gamma). The transduction efficacy of the HD-Ad vector in woodchuck liver in vivo was tested with a vector expressing green fluorescence protein (GFP). Immunohistochemical staining of liver samples on day 5 after injection showed expression of GFP in a high percentage of liver cells surrounding the central vein. The transduction of livers of WHV carriers in vivo with HD-AdwIFN-alpha or HD-AdwIFN-gamma induced levels of biologically active IFN, which could be measured in the sera of these animals. Expression of wIFN-alpha in the liver reduced intrahepatic WHV replication and WHV DNA in sera of about 1 log step in two of two woodchucks. Transduction with HD-AdwIFN-gamma, however, reduced WHV replicative intermediates only slightly in two of three animals, which was not accompanied with significant changes in the WHV DNA in sera. We demonstrated for the first time the successful HD-Ad vector-mediated transfer of genes for IFN-alpha and IFN-gamma in vivo and timely limited reduction of WHV replication by wIFN-alpha, but not by wIFN-gamma.