Rheological study of interactions between non-ionic surfactants and polysaccharide thickeners used in textile printing

The influence of four non-ionic surfactants (isododecyl and cetyl polyoxyethylene ethers) on aqueous polysaccharide solutions (sodium alginate, guar gum, and sodium carboxymethyl guar), applicable for textile printing pastes, were studied via rheological measurements.

Rheology of polysaccharide–surfactant solutions in aqueous matrices is primarily governed by polymer content, which imparts marked shear-thinning and viscoelastic character to the system. Such properties are modulated in moderate but sensible way by changes in surfactant concentration or type. Above 3% surfactants addition to non-substituted guar gum solutions results in a significant impact leading to phase separation and a particular strongly associated phase is formed due to hydrogen bonds between ethylene oxy units from the surfactant and primary hydroxyl groups in guar.

A satisfactory fitting of viscosity data is obtained with both the Cross equation and the Roberts–Barnes–Carew model. The experimental results of mechanical spectra can be described quite satisfactory with both the Friedrich–Braun and the generalized Maxwell models.     

<Emphasis Type="Italic">Arabidopsis thaliana</Emphasis> AtGpp1 and AtGpp2: two novel low molecular weight phosphatases involved in plant glycerol metabolism

We have isolated two Arabidopsis thaliana genes, AtGpp1 and AtGpp2, showing homology with the yeast low molecular weight phosphatases GPP1 and GPP2, which have a high specificity for dl-glycerol-3-phosphate, and moreover homology with DOG1 and DOG2 that dephosphorylate 2-deoxyglucose-6-phosphate. Using a comparative genomic approach, the corresponding genes were identified as conceptual translated haloacid dehalogenase-like hydrolase proteins. AtGpp1 (gi 18416631) and AtGpp2 (gi 18423981), encode proteins that share 95% identity, with a predicted Mw of 33 and 27 kDa and a pI of 7.8 and 5.6, respectively. Both isoforms have a high specificity for dl-glycerol-3-phosphate, pH optima at 7.0, and K _m in the range of 3.5–5.2 mM. AtGpp1 and AtGpp2 are expressed throughout development in all plant organs, most strongly in siliqua, and expression is not affected by osmotic, ionic or oxidative stress. A putative chloroplast transit peptide cTP-containing sequence is appended to the AtGpp1 N-terminus while AtGpp2, devoid of this tail, is predicted to be in the extraplastidial cytosol; this compartmenting was further confirmed by subcellular fractionation. An immunohystochemical localization study, using anti-AtGpp2 antibodies, indicates that the AtGpp proteins are mainly restricted to the meristem of immature flower and vascular elements of the root, shoot, leave, siliqua and developing embryo. Considerable immunoreaction was observed in the cytoplasm as well as in plastid compartments of distinct cells types from different heterotrophic Arabidopsis tissues, and particularly localised within phloem companion cells. Transgenic Arabidopsis plants, with gain of AtGpp2 function, show altered phosphatase activity rates and improved tolerance to salt, osmotic and oxidative stress.     

MAPK pathway mediates muscarinic receptor-induced human lung fibroblast proliferation

Airway remodelling is a pathological feature of chronic inflammatory and obstructive airway diseases like asthma and COPD wherein fibroblasts contribute to structural alteration processes. We recently reported expression of multiple muscarinic receptors in human lung fibroblasts and demonstrated muscarinic receptor-induced, G(i)-mediated proliferation in these cells. We now explore the underlying intracellular signalling pathways. As a measure of cell proliferation ((3)H)-thymidine incorporation in primary human lung fibroblasts and MRC-5 fibroblasts was increased by about 2 fold in presence of the muscarinic receptor agonist carbachol (10 microM) and this effect could be prevented by the MEK inhibitor PD 98059 (30 microM). Western blot analysis revealed a rapid (within 2 min) activation of p42/44 MAPK (ERK1, ERK2) following exposure to 10 microM carbachol or oxotremorine, effects blocked by tiotropium as well as atropine. In conclusion, the proliferative response of lung fibroblasts to muscarine receptor stimulation is mediated via activation of the classical MEK-ERK MAPK cascade. It is suggested that prevention of cholinergic driven fibroblast proliferation by prolonged blockade of airway muscarinic receptors may contribute to the reported long term beneficial effects of anticholinergics.     

GST genotypes and lung cancer susceptibility in Asian populations with indoor air pollution exposures: a meta-analysis

About half of the world's population is exposed to smoke from heating or cooking with coal, wood, or biomass. These exposures, and fumes from cooking oil use, have been associated with increased lung cancer risk. Glutathione S-transferases play an important role in the detoxification of a wide range of human carcinogens in these exposures. Functional polymorphisms have been identified in the GSTM1, GSTT1, and GSTP1 genes, which may alter the risk of lung cancer among individuals exposed to coal, wood, and biomass smoke, and cooking oil fumes. We performed a meta-analysis of 6 published studies (912 cases; 1063 controls) from regions in Asia where indoor air pollution makes a substantial contribution to lung cancer risk, and evaluated the association between the GSTM1 null, GSTT1 null, and GSTP1 105Val polymorphisms and lung cancer risk. Using a random effects model, we found that carriers of the GSTM1 null genotype had a borderline significant increased lung cancer risk (odds ratio (OR), 1.31; 95% confidence interval (CI), 0.95-1.79; p=0.10), which was particularly evident in the summary risk estimate for the four studies carried out in regions of Asia that use coal for heating and cooking (OR, 1.64; 95% CI, 1.25-2.14; p=0.0003). The GSTT1 null genotype was also associated with an increased lung cancer risk (OR, 1.49; 95% CI, 1.17-1.89; p=0.001), but no association was observed for the GSTP1 105Val allele. Previous meta- and pooled-analyses suggest at most a small association between the GSTM1 null genotype and lung cancer risk in populations where the vast majority of lung cancer is attributed to tobacco, and where indoor air pollution from domestic heating and cooking is much less than in developing Asian countries. Our results suggest that the GSTM1 null genotype may be associated with a more substantial risk of lung cancer in populations with coal exposure.     

Structural analysis and dynamics of retinal chromophore in dark and meta I states of rhodopsin from 2H NMR of aligned membranes

Rhodopsin is a prototype for G protein-coupled receptors (GPCRs) that are implicated in many biological responses in humans. A site-directed (2)H NMR approach was used for structural analysis of retinal within its binding cavity in the dark and pre-activated meta I states. Retinal was labeled with (2)H at the C5, C9, or C13 methyl groups by total synthesis, and was used to regenerate the opsin apoprotein. Solid-state (2)H NMR spectra were acquired for aligned membranes in the low-temperature lipid gel phase versus the tilt angle to the magnetic field. Data reduction assumed a static uniaxial distribution, and gave the retinylidene methyl bond orientations plus the alignment disorder (mosaic spread). The dark-state (2)H NMR structure of 11-cis-retinal shows torsional twisting of the polyene chain and the beta-ionone ring. The ligand undergoes restricted motion, as evinced by order parameters of approximately 0.9 for the spinning C-C(2)H(3) groups, with off-axial fluctuations of approximately 15 degrees . Retinal is accommodated within the rhodopsin binding pocket with a negative pre-twist about the C11=C12 double bond that explains its rapid photochemistry and the trajectory of 11-cis to trans isomerization. In the cryo-trapped meta I state, the (2)H NMR structure shows a reduction of the polyene strain, while torsional twisting of the beta-ionone ring is maintained. Distortion of the retinal conformation is interpreted through substituent control of receptor activation. Steric hindrance between trans retinal and Trp265 can trigger formation of the subsequent activated meta II state. Our results are pertinent to quantum and molecular mechanics simulations of ligands bound to GPCRs, and illustrate how (2)H NMR can be applied to study their biological mechanisms of action.     

Sequence elements in both subunits of the DNA fragmentation factor are essential for its nuclear transport

DNA cleavage is a biochemical hallmark of apoptosis. In humans, apoptotic DNA cleavage is executed by DNA fragmentation factor (DFF) 40. In proliferating cells DFF40 is expressed in the presence of its chaperone and inhibitor DFF45, which results in the formation of the DFF complex. Here, we present a systematic analysis of the nuclear import of the DFF complex. Our in vitro experiments demonstrate that the importin alpha/beta-heterodimer mediates the translocation of the DFF complex from the cytoplasm to the nucleus. Both DFF subunits interact directly with the importin alpha/beta-heterodimer. However, importin alpha/beta binds more tightly to the DFF complex compared with the individual subunits. Additionally, the isolated C-terminal regions of both DFF subunits together bind importin alpha/beta more strongly than the individual C termini. Our results from in vivo studies reveal that the C-terminal regions of both DFF subunits harbor nuclear localization signals. Furthermore, nuclear import of the DFF complex requires the C-terminal regions of both subunits. In more detail, one basic cluster in the C-terminal region of each subunit, DFF40 (RLKRK) and DFF45 (KRAR), is essential for nuclear accumulation of the DFF complex. Based on these findings two alternative models for the interaction of importin alpha/beta with the DFF complex are presented.     

Bak and Bax are non-redundant during infection- and DNA damage-induced apoptosis

Mitochondrial outer membrane permeabilization (MOMP) and release of mitochondrial intermembrane proteins like cytochrome c are critical steps in the control of apoptosis. Previous work has shown that MOMP depends on the functionally redundant multidomain proapoptotic proteins, Bak and Bax. Here we demonstrate that Bak and Bax are functionally non-redundant during Neisseria gonorrhoeae (Ngo)- and cisplatin-induced apoptosis. While the activation of Bak is caspase independent Bax activation needs Bak and active caspases. Silencing of either Bak or Bax resists both Ngo- and cisplatin- but not TNFalpha-induced apoptosis. Activation of Bak is required to release cytochrome c from the mitochondria; however, Bax is still required to activate effector caspases. Thus, both Bak and Bax are necessary to accomplish DNA damage and Ngo-induced apoptosis.     

Computational analysis of CFSE proliferation assay

CFSE based tracking of the lymphocyte proliferation using flow cytometry is a powerful experimental technique in immunology allowing for the tracing of labelled cell populations over time in terms of the number of divisions cells undergone. Interpretation and understanding of such population data can be greatly improved through the use of mathematical modelling. We apply a heterogenous linear compartmental model, described by a system of ordinary differential equations similar to those proposed by Kendall. This model allows division number-dependent rates of cell proliferation and death and describes the rate of changes in the numbers of cells having undergone j divisions. The experimental data set that we specifically analyze specifies the following characteristics of the kinetics of PHA-induced human T lymphocyte proliferation assay in vitroL (1) the total number of live cells, (2) the total number of dead but not disintegrated cells and (3) the number of cells divided j times. Following the maximum likelihood approach for data fitting, we estimate the model parameters which, in particular, present the CTL birth- and death rate “functions”. It is the first study of CFSE labelling data which convincingly shows that the lymphocyte proliferation and death both in vitro and in vivo are division number dependent. For the first time, the confidence in the estimated parameter values is analyzed by comparing three major methods: the technique based on the variance–covariance matrix, the profile-likelihood-based approach and the bootstrap technique. We compare results and performance of these methods with respect to their robustness and computational cost. We show that for evaluating mathematical models of differing complexity the information-theoretic approach, based upon indicators measuring the information loss for a particular model (Kullback–Leibler information), provides a consistent basis. We specifically discuss methodological and computational difficulties in parameter identification with CFSE data, e.g. the loss of confidence in the parameter estimates starting around the sixth division. Overall, our study suggests that the heterogeneity inherent in cell kinetics should be explicitly incorporated into the structure of mathematical models.      

Photosynthetic efficiency as a function of thermal stratification and phytoplankton size structure in an oligotrophic alpine lake

Allometric relationships of phytoplankton communities were studied on the basis of a five-year data-set in a deep oligotrophic alpine lake in Austria. The seasonal phytoplankton succession in Mondsee is characterised by diatoms during winter mixing and a distinct metalimnetic population of Planktothrix rubescens during stratification in summer. The variation of phytoplankton photosynthetic efficiency between seasons was assessed using in situ carbon-uptake rates (5 years data) and Fast Repetition Rate Fluorometry (FRRF) (2 years data). The light-saturated, chlorophyll-specific rate of photosynthesis (P*_max), irradiance at the onset of saturation (E _k) and maximum light-utilisation efficiency (α*) were determined for winter mixing and summer stratification. Fluorescence-based parameters as the functional absorption cross section of Photosystem II (σ _PSII) and the photochemical quantum yield (F _v/F _m) were additionally analysed in 2003 and 2004 to study the underlying physiological mechanisms for the variability in photosynthetic performance. Beyond their sensitivity to changing environmental conditions like thermal stratification, phytoplankton populations differ in their photosynthetic behaviour according to their size structure. Therefore Photosynthesis vs. Irradiance (P/E)-relationships were analysed in detail within a 1-year period from size fractionated cell counts, chlorophyll-a and carbon-uptake.