The mitochondrial tricarboxylate carrier of silver eel: chemical modification by sulfhydryl reagents

The tricarboxylate (or citrate) carrier was purified from eel liver mitochondria and functionally reconstituted into liposomes. Incubation of the proteoliposomes with various sulfhydryl reagents led to inhibition of the reconstituted citrate transport activity. Preincubation of the proteoliposomes with reversible SH reagents, such as mercurials and methanethiosulfonates, protected the eel liver tricarboxylate carrier against inactivation by the irreversible reagent N-(1-pyrenyl)maleimide (PM). Citrate and L-malate, two substrates of the tricarboxylate carrier, protected the protein against inactivation by sulfhydryl reagents and decreased the fluorescent PM bound to the purified protein. These results suggest that the eel liver tricarboxylate carrier requires a single population of free cysteine(s) in order to manifest catalytic activity. The reactive cysteine(s) is most probably located at or near the substrate binding site of the carrier protein.     

Immune activation and CD8+ T-cell differentiation towards senescence in HIV-1 infection

Progress in the fight against the HIV/AIDS epidemic is hindered by our failure to elucidate the precise reasons for the onset of immunodeficiency in HIV-1 infection. Increasing evidence suggests that elevated immune activation is associated with poor outcome in HIV-1 pathogenesis. However, the basis of this association remains unclear. Through ex vivo analysis of virus-specific CD8⁺ T-cells and the use of an in vitro model of naïve CD8⁺ T-cell priming, we show that the activation level and the differentiation state of T-cells are closely related. Acute HIV-1 infection induces massive activation of CD8⁺ T-cells, affecting many cell populations, not only those specific for HIV-1, which results in further differentiation of these cells. HIV disease progression correlates with increased proportions of highly differentiated CD8⁺ T-cells, which exhibit characteristics of replicative senescence and probably indicate a decline in T-cell competence of the infected person. The differentiation of CD8⁺ and CD4⁺ T-cells towards a state of replicative senescence is a natural process. It can be driven by excessive levels of immune stimulation. This may be part of the mechanism through which HIV-1-mediated immune activation exhausts the capacity of the immune system.     

Regulation of DNA replication by ATR: signaling in response to DNA intermediates

The nuclear protein kinase ATR controls S-phase progression in response to DNA damage and replication fork stalling, including damage caused by ultraviolet irradiation, hyperoxia, and replication inhibitors like aphidicolin and hydroxyurea. ATR activation and substrate specificity require the presence of adapter and mediator molecules, ultimately resulting in the downstream inhibition of the S-phase kinases that function to initiate DNA replication at origins of replication. The data reviewed strongly support the hypothesis that ATR is activated in response to persistent RPA-bound single-stranded DNA, a common intermediate of unstressed and damaged DNA replication and metabolism.     

3-Amino derivative of beta-cyclodextrin: thermodynamics of copper(II) complexes and exploitation of its enantioselectivity in the separation of amino acid racemates by ligand exchange capillary electrophoresis

The systems that the 3-amino derivative of beta-cyclodextrin (CD3NH2) forms with the proton, the copper(II) ion and each of the enantiomers of certain amino acids (alanine, phenylalanine, tyrosine and tryptophan) were investigated. The enantioselectivity shown by the potentiometric measurements carried out on the phenylalanine ternary systems was exploited in capillary electrophoresis by ligand exchange capillary electrophoresis (LECE) to obtain the separation of phenylalanine racemate. The tyrosine racemate was also separated by LECE. The comparison between thermodynamic and capillary electrophoresis (CE) results is discussed, in order to get a better insight into the separation mechanism.     

Role of anti-cyclic citrullinated peptide antibodies in discriminating patients with rheumatoid arthritis from patients with chronic hepatitis C infection-associated polyarticular involvement

This study was performed to assess the utility of anti-cyclic citrullinated peptide (anti-CCP) antibodies in distinguishing between patients with rheumatoid arthritis (RA) and patients with polyarticular involvement associated with chronic hepatitis C virus (HCV) infection. Serum anti-CCP antibodies and rheumatoid factor (RF) were evaluated in 30 patients with RA, 8 patients with chronic HCV infection and associated articular involvement and 31 patients with chronic HCV infection without any joint involvement. In addition, we retrospectively analysed sera collected at the time of first visit in 10 patients originally presenting with symmetric polyarthritis and HCV and subsequently developing well-established RA. Anti-CCP antibodies and RF were detected by commercial second-generation anti-CCP2 enzyme-linked immunosorbent assay and immunonephelometry respectively. Anti-CCP antibodies were detected in 23 of 30 (76.6%) patients with RA but not in patients with chronic HCV infection irrespective of the presence of articular involvement. Conversely, RF was detected in 27 of 30 (90%) patients with RA, 3 of 8 (37.5%) patients with HCV-related arthropathy and 3 of 31 (9.7%) patients with HCV infection without joint involvement. Finally, anti-CCP antibodies were retrospectively detected in 6 of 10 (60%) patients with RA and HCV. This indicates that anti-CCP antibodies can be useful in discriminating patients with RA from patients with HCV-associated arthropathy.     

Dynamical aspects of P systems

A dynamical analysis of P systems is given that is focused on basic phenomena of biological relevance. After a short presentation of a new kind of P systems (PB systems), membrane systems with environment, called PBE systems, are introduced that are more suitable for modeling complex membrane interactions. Some types of periodicity and non-periodicity are considered for PBE systems by showing some "minimal" examples of systems that exhibit these properties. In particular, a discrete formulation of the Belousov-Zhabotinsky (BZ) reaction is given in terms of PBE systems. Some questions and open problems for future research are indicated.     

Homologues and isomers of noladin ether,a putative novel endocannabinoid: interaction with rat cannabinoid CB(1) receptors

Two regioisomers and 13 analogues of the putative endocannabinoid noladin ether (2-arachidonyl glyceryl ether, 2-AGE, 1) were synthesized and tested for their interaction with CB(1) receptors in rat brain membranes. The results showed that a C-20 tetra-unsaturated moiety is necessary for high affinity, and that a series of alkyl glyceryl ethers of potential occurrence in brain tissues have less affinity than 2-AGE for CB(1) receptors.     

Cdk2 knockout mice are viable

BACKGROUND: Cyclin-dependent kinases (Cdks) and their cyclin regulatory subunits control cell growth and division. Cdk2/cyclin E complexes are thought to be required because they phosphorylate the retinoblastoma protein and drive cells through the G1/S transition into the S phase of the cell cycle. In addition, Cdk2 associates with cyclin A, which itself is essential for cell proliferation during early embryonic development. RESULTS: In order to study the functions of Cdk2 in vivo, we generated Cdk2 knockout mice. Surprisingly, these mice are viable, and therefore Cdk2 is not an essential gene in the mouse. However, Cdk2 is required for germ cell development; both male and female Cdk2(-/-) mice are sterile. Immunoprecipitates of cyclin E1 complexes from Cdk2(-/-) spleen extracts displayed no activity toward histone H1. Cyclin A2 complexes were active in primary mouse embryonic fibroblasts (MEFs), embryo extracts and in spleen extracts from young animals. In contrast, there was little cyclin A2 kinase activity in immortalized MEFs and spleen extracts from adult animals. Cdk2(-/-) MEFs proliferate but enter delayed into S phase. Ectopic expression of Cdk2 in Cdk2(-/-) MEFs rescued the delayed entry into S phase. CONCLUSIONS: Although Cdk2 is not an essential gene in the mouse, it is required for germ cell development and meiosis. Loss of Cdk2 affects the timing of S phase, suggesting that Cdk2 is involved in regulating progression through the mitotic cell cycle.