Relationship of the Surface Structure of Metaphase Chromosomes to the Higher Order Organization of Chromatin Fibers

Scanning electron microscopy (SEM), as well as transmission electron microscopy (TEM), has been utilized to determine how the surface structure of mitotic chromosomes is related to the organization of the 30 nm chromosomal fibers. SEM revealed the surfaces of isolated, HeLa cell chromosomes to possess a knobby substructure with chromosomes prepared for EM in buffers containing 0.5-1.5 mM Mg2+. These projections had substantially greater widths (65-70 nm) than the underlying chromatin fibers. Reducing the Mg ion concentration to 0.05-0.15 mM resulted in the further expansion of the chromosomes, which flattened the chromosomes for SEM so the fibers became the dominant feature of the micrographs. The surface protuberances are interpreted as representing the peripheral tips of radial chromatin loops. The same procedure of slightly expanding chromosomes by decreasing the Mg2+ concentration in resuspension buffer was also utilized in a TEM, serial sectioning study. Longitudinal sections close to the central chromatid axis showed radially oriented fibers within the planes of the sections. This was replaced by a dot pattern when the longitudinal sections grazed the periphery of the chromatid. Transverse sections displayed more clearly the radial orientation of the fibers. A consistent picture emerges from applying SEM and TEM that supports the radial loop model for the primary mode of organization of chromatin fibers in metaphase chromosomes

Immunomics in inflammatory rheumatic diseases

Autoimmune diseases such as rheumatoid arthritis (RA) are characterized by autoantibodies to different autoantigenic proteins. Using proteomic 2D immunoblots, we identified a new 40 kDa autoantigen – hnRNP A3 – from HeLa nuclear extracts, which is frequently (30%) detected by RA. Moreover, we used a set of protein arrays of about 50 000 proteins derived from a human foetal brain cDNA expression library for screening with patient sera. Additionally, we utilized a human foetal brain cDNA library in a robot-based T7 phage display screening system with RA patient sera. To determine the diversity of the enriched library, we amplified the cDNA inserts and hybridized them onto the custom-made human ENSEMBL cDNA array. By these methods, over 80 clones were identified to bind patient immunoglobulins. Moreover, nine clones show only IgA-specific reactivity. We have now evaluated two different clones thoroughly: the carboxyl-terminal half of the nucleolar phosphoprotein p130 (NOPP 130) and a clone representing a 41-amino-acid mimetic peptide showing homology to calreticulin, a previously reported autoantigen. The remaining proteins are still undergoing thorough investigation. Applying state-of-the-art proteomic techniques, such as protein array and phage display, we have succeeded in identifying more than 80 potentially autoantigenic marker molecules, of which we have characterized a subset for RA specificity by screening with large numbers of patient and control sera. However, none of the molecules characterized thus far is exclusively discriminatory for RA and they all exhibit overlap with other autoimmune diseases

Does the future look bright? Processing style determines the impact of valence weighting biases and self-beliefs on expectations

People regularly form expectations about their future, and whether those expectations are positive or negative can have important consequences. So, what determines the valence of people’s expectations? Research seeking to answer this question by using an individual-differences approach has established that trait biases in optimistic/pessimistic self-beliefs and, more recently, trait biases in behavioral tendencies to weight one’s past positive versus negative experiences more heavily each predict the valence of people’s typical expectations. However, these two biases do not correlate, suggesting limits on a purely individual-differences approach to predicting people’s expectations. We hypothesize that, because these two biases appear to operate via distinct processes (with self-beliefs operating top-down and valence weighting bias operating bottom-up), to predict a person’s expectations on a given occasion, it is also critical to consider situational factors influencing processing style. To test this hypothesis, we investigated how an integral part of future thinking that influences processing style—mental imagery—determines each bias’s influence. Two experiments measured valence weighting biases and optimistic/pessimistic self-beliefs, then manipulated whether participants formed expectations using their own first-person visual perspective (which facilitates bottom-up processes) or an external third-person visual perspective (which facilitates top-down processes). Expectations corresponded more with valence weighting biases from the first-person (vs. third-person) but more with self-beliefs from the third-person (vs. first-person). Two additional experiments manipulated valence weighting bias, demonstrating its causal role in shaping expectations (and behaviors) with first-person, but not third-person, imagery. These results suggest the two biases operate via distinct processes, holding implications for interventions to increase optimism

Lipid emulsions – Guidelines on Parenteral Nutrition, Chapter 6

The infusion of lipid emulsions allows a high energy supply, facilitates the prevention of high glucose infusion rates and is indispensable for the supply with essential fatty acids. The administration of lipid emulsions is recommended within ≤7 days after starting PN (parenteral nutrition) to avoid deficiency of essential fatty acids. Low-fat PN with a high glucose intake increases the risk of hyperglycaemia. In parenterally fed patients with a tendency to hyperglycaemia, an increase in the lipid-glucose ratio should be considered. In critically ill patients the glucose infusion should not exceed 50% of energy intake. The use of lipid emulsions with a low phospholipid/triglyceride ratio is recommended and should be provided with the usual PN to prevent depletion of essential fatty acids, lower the risk of hyperglycaemia, and prevent hepatic steatosis. Biologically active vitamin E (α-tocopherol) should continuously be administered along with lipid emulsions to reduce lipid peroxidation. Parenteral lipids should provide about 25–40% of the parenteral non-protein energy supply. In certain situations (i.e. critically ill, respiratory insufficiency) a lipid intake of up to 50 or 60% of non-protein energy may be reasonable. The recommended daily dose for parenteral lipids in adults is 0.7–1.3 g triglycerides/kg body weight. Serum triglyceride concentrations should be monitored regularly with dosage reduction at levels >400 mg/dl (>4.6 mmol/l) and interruption of lipid infusion at levels >1000 mg/dl (>11.4 mmol/l). There is little evidence at this time that the choice of different available lipid emulsions affects clinical endpoints

Imaging Molecular Structure through Femtosecond Photoelectron Diffraction on Aligned and Oriented Gas-Phase Molecules

This paper gives an account of our progress towards performing femtosecond time-resolved photoelectron diffraction on gas-phase molecules in a pump-probe setup combining optical lasers and an X-ray Free-Electron Laser. We present results of two experiments aimed at measuring photoelectron angular distributions of laser-aligned 1-ethynyl-4-fluorobenzene (C8H5F) and dissociating, laseraligned 1,4-dibromobenzene (C6H4Br2) molecules and discuss them in the larger context of photoelectron diffraction on gas-phase molecules. We also show how the strong nanosecond laser pulse used for adiabatically laser-aligning the molecules influences the measured electron and ion spectra and angular distributions, and discuss how this may affect the outcome of future time-resolved photoelectron diffraction experiments.Comment: 24 pages, 10 figures, Faraday Discussions 17

Exclusive rho^0 muoproduction on transversely polarised protons and deuterons

The transverse target spin azimuthal asymmetry A_UT in hard exclusive production of rho^0 mesons was measured at COMPASS by scattering 160 GeV/c muons off transversely polarised protons and deuterons. The measured asymmetry is sensitive to the nucleon helicity-flip generalised parton distributions E^q, which are related to the orbital angular momentum of quarks in the nucleon. The Q^2, x_B and p_t^2 dependence of A_UT is presented in a wide kinematic range. Results for deuterons are obtained for the first time. The measured asymmetry is small in the whole kinematic range for both protons and deuterons, which is consistent with the theoretical interpretation that contributions from GPDs E^u and E^d approximately cancel.Comment: 20 pages, 9 figures and 4 tables, updated author lis