Properties of a second epitope of the murine Fc receptor for aggregated IgG

The murine macrophage and lymphocyte Fc receptor for aggregated IgG (Fc gamma R) has previously been characterized by using the anti-Fc gamma R monoclonal antibody (mAb), 2.4G2. In the studies presented here, we describe a new mAb, 6B7C, that defines a second epitope of the Fc gamma R. The tissue distribution of the 6B7C epitope is coincident with the 2.4G2 epitope. However, only the 2.4G2 epitope is accessible to mAb binding on intact primary macrophages or lymphocytes. The 6B7C epitope is not detectable on primary macrophages or lymphocytes but is exposed on a portion of B lymphocyte Fc gamma R after activation by lipopolysaccharide and on some tumor cell lines. The expression of the 6B7C epitope on the surface of B lymphoblasts and tumor cell lines seems to correlate with their ability to release soluble Fc gamma R. The 6B7C mAb has the advantage that it reacts with native as well as denatured receptor and therefore can be used for techniques such as immunoblotting.     

Metabolic-network-driven analysis of bacterial ecological strategies

Background  

The growth-rate of an organism is an important phenotypic trait, directly affecting its ability to survive in a given environment. Here we present the first large scale computational study of the association between ecological strategies and growth rate across 113 bacterial species, occupying a variety of metabolic habitats. Genomic data are used to reconstruct the species' metabolic networks and habitable metabolic environments. These reconstructions are then used to investigate the typical ecological strategies taken by organisms in terms of two basic species-specific measures: metabolic variability - the ability of a species to survive in a variety of different environments; and co-habitation score vector - the distribution of other species that co-inhabit each environment.     

Metabolic innovations towards the human lineage

Background  

We describe a function-driven approach to the analysis of metabolism which takes into account the phylogenetic origin of biochemical reactions to reveal subtle lineage-specific metabolic innovations, undetectable by more traditional methods based on sequence comparison. The origins of reactions and thus entire pathways are inferred using a simple taxonomic classification scheme that describes the evolutionary course of events towards the lineage of interest. We investigate the evolutionary history of the human metabolic network extracted from a metabolic database, construct a network of interconnected pathways and classify this network according to the taxonomic categories representing eukaryotes, metazoa and vertebrates.     

Effects of coexpression of the LDL receptor and apoE on cholesterol metabolism and atherosclerosis in LDL receptor-deficient mice

The low density lipoprotein receptor (LDLR) plays a major role in regulation of plasma cholesterol levels as a ligand for apolipoprotein B-100 and apolipoprotein E (apoE). Consequently, LDLR-deficient mice fed a Western-type diet develop significant hypercholesterolemia and atherosclerosis. ApoE not only mediates uptake of atherogenic lipoproteins via the LDLR and other cell-surface receptors, but also directly inhibits atherosclerosis. In this study, we examined the hypothesis that coexpression of the LDLR and apoE would have greater effects than either one alone on plasma cholesterol levels and the development of atherosclerosis in LDLR-deficient mice. LDLR-deficient mice fed a Western-type diet for 10 weeks were injected with recombinant adenoviral vectors encoding the genes for human LDLR, human apoE3, both LDLR and apoE3, or lacZ (control). Plasma lipids were analyzed at several time points after vector injection. Six weeks after injection, mice were analyzed for extent of atherosclerosis by two independent methods. As expected, LDLR expression alone induced a significant reduction in plasma cholesterol due to reduced VLDL and LDL cholesterol levels, whereas overexpression of apoE alone did not reduce plasma cholesterol levels. When the LDLR and apoE were coexpressed in this model, the effects on plasma cholesterol levels were no greater than with expression of the LDLR alone. However, coexpression did result in a substantial increase in large apoE-rich HDL particles. In addition, although the combination of cholesterol reduction and apoE expression significantly reduced atherosclerosis, its effects were no greater than with expression of the LDLR or apoE alone. In summary, in this LDLR-deficient mouse model fed a Western-type diet, there was no evidence of an additive effect of expression of the LDLR and apoE on cholesterol reduction or atherosclerosis.     

Induction of murine B cell proliferation by insolubilized anti-immunoglobulins

This study demonstrates that intact antibodies specific for mu, delta, or light chains when coupled to Sepharose are effective in delivering proliferative signals to B cells. Furthermore, using Sepharose-coupled anti-delta antibodies, we have shown that hybridoma anti-delta (that is not active as soluble protein) is as effective as rabbit anti-delta in activating murine B cells. However, antibodies directed against two other surface molecules, I-A and H-2K, were not mitogenic. Thus, sIgM and sIgD are comparable in their ability to transmit a proliferative signal to the B cell and sIg seems to play a unique role in this regard.     

The effect of dimerization on the interaction of ibuprofen drug with calf thymus DNA: Molecularmodeling and spectroscopic investigation

The interaction between the dimer structure of ibuprofen drug (D-IB) and calf thymus DNA under simulative physiological conditions was investigated with the use of Hoechst 33258 and methylene blue dye as spectral probes by the methods of UV-visible absorption, fluorescence spectroscopy, circular dichroism spectroscopy and molecular modeling study.Using the Job's plot, a single class of binding sites for theD-IB on DNA was put in evidence. The Stern–Volmer analysis of fluorescence quenching data shows the presence of both the static and dynamic quenching mechanisms. The binding constants, K_b were calculated at different temperatures, and the thermodynamic parameters ?G^°, ?H^° and ?S^° were given. The experimental results showed that D-IB molecules could bind with DNA via groove binding mode as evidenced by: I. DNA binding constant from spectrophotometric studies of the interaction of D-IB with DNA is comparable to groove binding drugs. II. Competitive fluorimetric studies with Hoechst 33258 have shown that D-IB exhibits the ability of this complex to displace with DNA-bounded Hoechst, indicating that it binds to DNA in strong competition with Hoechst for the groove binding. III. There is no significantly change in the absorption of the MB-DNA system upon adding the D-IB, indicates that MB molecules are not released from the DNA helix after addition of the D-IB and are indicative of a non-intercalative mode of binding. IV. Small changes in DNA viscosity in the presence of D-IB, indicating weak link to DNA, which is consistent with DNA groove binding. As well as, induced CD spectral changes, and the docking results revealed that groove mechanism is followed by D-IB to bind with DNA.