Dichotomous effect of monocyte Fc receptor interaction on anti-CD3-induced immunoglobulin synthesis

Monoclonal antibodies against the TCR/CD3 complex are capable of activating T cells which in turn may induce immunoglobulin synthesis in B cells under appropriate conditions. Here we present evidence that distinct immune responses, induced by four commonly used TCR/CD3 mAb (Leu4, OKT3, BMA030, BMA031) were related to the mAb interaction with monocyte Fc receptors for IgG. Depending on their isotype and on the technique by which they were crosslinked, TCR/CD3 mAb induced variable IgM and IgG synthesis in PBMC: If the mAb were crosslinked by monocyte IgG-Fc receptors they induced a high Ig production, while crosslinking the same mAb by plastic-bound goat anti-mouse antibodies (panning) failed to do so. Nevertheless, both crosslinking techniques triggered a strong proliferation and IL-2, IL-4, and IFN gamma lymphokine gene expression. The lack of Ig production under panning conditions was due to an additional IgG-Fc receptor interaction with monocytes: (a) If namely mAb F(ab')2 fragments, or mAb isotypes unable to bind to monocyte Fc receptors (IgG2b, IgG1 in nonresponders) were crosslinked by panning, both a good proliferation as well as Ig production ensued; (b) if TCR/CD3 mAb isotypes which could additionally bind to monocyte Fc receptor (IgG2a) were crosslinked, no Ig production occurred; (c) if mAb F(ab')2 fragments were crosslinked with a second anti-T cell antibody of IgG2a isotype, which could bind to monocyte Fc receptors, Ig synthesis was reduced. Interestingly enough, this diminishing effect, due to monocyte Fc receptor interaction, was only observed if CD4-positive cells were proliferating, but not if CD8-positive cells were activated.     

Crystal structure of Aspergillus niger pH 2.5 acid phosphatase at 2. 4 A resolution.

The crystal structure of Aspergillus niger pH 2.5 acid phosphatase (EC 3.1.3.2) has been determined at 2.4 A resolution. In the crystal, two dimers form a tetramer in which the active sites are easily accessible to substrates. The main contacts in the dimer come from the N termini, each lying on the surface of the neighbouring molecule. The monomer consists of two domains, with the active site located at their interface. The active site has a highly conserved catalytic center and a charge distribution, which explains the highly acidic pH optimum and the broad substrate specificity of the enzyme.     

Novel ketolide antibiotics with a fused five-membered lactone ring--synthesis, physicochemical and antimicrobial properties

In an effort to find novel semisynthetic macrolides with extended antibacterial spectrum and improved activity we prepared a series of compounds based on commercially available clarithromycin, a potent and safe antimicrobial agent of outstanding clinical and commercial interest. According to the literature, improvement of antibacterial activity of erythromycin type antibiotics can be achieved by introduction of fused heterocycles such as cyclic carbonates or carbamates at positions 11 and 12 (such as in telithromycin). In the course of the work presented here, a similar, hitherto unprecedented set of compounds bearing a five-membered lactone ring fused to positions 11 and 12 was prepared based on carbon-carbon bond formation via intramolecular Michael addition of a [(hetero)arylalkylthio]acetic acid ester enolate to an alpha,beta-unsaturated ketone as the key step. Some of the ketolide compounds described in this paper were highly active against a representative set of erythromycin sensitive and erythromycin resistant test strains. The best compound showed a similar antimicrobial spectrum and comparable activity in vitro as well as in vivo as telithromycin. Furthermore, some physicochemical properties of these compounds were determined and are presented here. On the basis of these results, the novel ketolide lactones presented in this paper emerged as valuable lead compounds with comparable properties as the commercial ketolide antibacterial telithromycin (Ketek).     

Circadian rhythm of plasma sodium is disrupted in spontaneously hypertensive rats fed a high-NaCl diet

High-NaCl diets elevate arterial pressure in NaCl-sensitive individuals, and increases in plasma sodium may trigger this effect. The present study tests the hypotheses that 1) plasma sodium displays a circadian rhythm in rats, 2) the plasma sodium rhythm is disturbed in spontaneously hypertensive rats (SHR), and 3) excess dietary NaCl elevates plasma sodium concentration in SHR. The results demonstrate that plasma sodium has a circadian rhythm that is inversely related to the circadian rhythm of arterial pressure. Although the plasma sodium rhythms of SHR and control rats are nearly identical, the plasma sodium concentrations are significantly higher in SHR throughout the 24-h cycle. Maintenance on a high-NaCl diet increases plasma sodium concentration similarly in both SHR and control rats, but it blunts the plasma sodium rhythm only in SHR. These results demonstrate that in rats, plasma sodium has a circadian rhythm and that high-NaCl diets increase plasma sodium concentration.     

Fused bicyclic Gly-Asp beta-turn mimics with potent affinity for GPIIb-IIIa. Exploration of the arginine isostere

6-[4-Amidinobenzoyl]amino]-tetralone-2-acetic acid is a potent antagonist of GPIIb-IIIa. Substitution in the meta position of the benzamidine, or replacement with a heteroaryl amidine was tolerated in this series. Use of an acyl-linked 4-alkyl piperidine as an arginine isostere also provided active compounds. Compounds from this series provided substantial systemic exposure in the rat following oral administration.     

The highly conserved C-terminal dileucine motif in the cytosolic domain of the human immunodeficiency virus type 1 envelope glycoprotein is critical for its association with the AP-1 clathrin adaptor [correction of adapter

Short amino acid sequences in the cytosolic domains of transmembrane proteins are recognized by specialized adaptor [corrected] proteins which are part of coated vesicles utilized to transport membrane proteins between the trans-Golgi network (TGN) and the plasma membrane (forward and backward). Previously, we and others reported that the membrane-proximal tyrosine residues Y712 (human immunodeficiency virus [HIV]) and Y721 (simian immunodeficiency virus [SIV]) in the envelope glycoprotein (Env) of the primate lentiviruses are crucial for the association of Env with clathrin-associated adaptor [corrected] complex AP-2. The same tyrosine-based endocytosis motifs in the cytosolic domains (EnvCD) of transmembrane gp41 of HIV type 1 (HIV-1) and SIV, respectively, were also shown to modulate the interaction with TGN- and endosome-based clathrin-associated complex AP-1. Our findings suggested that EnvCD binding to AP-1, unlike the association of EnvCD with AP-2, is dependent largely on residues other than Y712 and Y721. Here, we tested if motifs downstream of Y712 affect HIV-1 EnvCD-AP-1 binding and Env trafficking. Mutational analysis revealed that the C-terminal leucine-based motif in Env was crucial for the recruitment of AP-1 in vitro and in Env-expressing cells. In addition to affecting Env-AP-1 association, mutations at the C terminus of Env also altered the subcellular localization of Env, suggesting that proper post-Golgi routing of Env depends on its recruitment of AP-1. Finally, the C-terminal dileucine was shown to assist the membrane-proximal Y712 motif in restricting the cell surface expression of Env.     

Synthesis and characterization of thermoset biodegradable elastomers based on star-poly(epsilon-caprolactone-co-D,L-lactide)

Biodegradable elastomers represent a useful class of biomaterials. In this paper, we synthesize thermoset elastomers by utilizing the living nature of ring-opening polymerization of a star copolymer of D,L-lactide and epsilon-caprolactone initiated with glycerol and catalyzed by stannous 2-ethylhexanoate. The star copolymers were synthesized of varying molecular weight and monomer composition and cross-linked by compression molding using a dilactone, bis(epsilon-caprolactone-4-yl)propane dissolved in epsilon-caprolactone monomer. The elastomers were then characterized by differential scanning calorimetry and uniaxial tensile testing and their physical properties related to the nature of the star copolymer prepolymers. The results demonstrate a means of predictably altering the elastomer physical properties by adjusting the star copolymer prepolymer initial molecular weight and monomer ratio.