Cytochrome c release and mitochondria involvement in programmed cell death induced by acetic acid in Saccharomyces cerevisiae

Evidence is presented that mitochondria are implicated in the previously described programmed cell death (PCD) process induced by acetic acid in Saccharomyces cerevisiae. In yeast cells undergoing a PCD process induced by acetic acid, translocation of cytochrome c (CytC) to the cytosol and reactive oxygen species production, two events known to be proapoptotic in mammals, were observed. Associated with these events, reduction in oxygen consumption and in mitochondrial membrane potential was found. Enzymatic assays showed that the activity of complex bc(1) was normal, whereas that of cytochrome c oxidase (COX) was strongly decreased. This decrease is in accordance with the observed reduction in the amounts of COX II subunit and of cytochromes a+a(3). The acetic acid-induced PCD process was found to be independent of oxidative phosphorylation because it was not inhibited by oligomycin treatment. The inability of S. cerevisiae mutant strains (lacking mitochondrial DNA, heme lyase, or ATPase) to undergo acetic acid-induced PCD and in the ATPase mutant (knockout in ATP10) the absence of CytC release provides further evidence that the process is mediated by a mitochondria-dependent apoptotic pathway. The understanding of the involvement of a mitochondria-dependent apoptotic pathway in S. cerevisiae PCD process will be most useful in the further elucidation of an ancestral pathway common to PCD in metazoans.     

Shortening of the Symptom-Free Period in Rhesus Macaques Is Associated with Decreasing Nonsynonymous Variation in the env Variable Regions of Simian Immunodeficiency Virus SIVsm during Passage

During six blood passages of simian immunodeficiency virus SIVsm in rhesus macaques, the asymptomatic period shortened from 18 months to 1 month. To study SIVsm envelope gene (env) evolution during passage in rhesus macaques, the C1 to CD4 binding regions of multiple clones were sequenced at seroconversion and again at death. The env variation found during adaptation was almost completely confined to the variable regions. Intrasample sequence variation among clones at seroconversion was lower than the variation among clones at death. Intrasample variation among clones from a single time point as well as intersample variation decreased during the passage. In the variable regions, the mean number of intrasample nonsynonymous nucleotide substitutions decreased from the first passage (5.26 × 10⁻² ± 0.6 × 10⁻² per site) to the fifth passage (2.24 × 10⁻² ± 0.4 × 10⁻² per site), whereas in the constant regions, the mean number of intrasample nonsynonymous nucleotide substitutions differed less between the first and fifth passages (1.14 × 10⁻² ± 0.27 × 10⁻² and 0.80 × 10⁻² ± 0.24 × 10⁻² per site). Shortening of the asymptomatic period coincided with a rise in the Ks/Ka ratio (ratio between the number of synonymous [Ks] and the number of nonsynonymous [Ka] substitutions) from 1.080 in passage one to 1.428 in passage five and mimicked the difference seen in the intrahost evolution between asymptomatic and fast-progressing individuals infected with human immunodeficiency virus type 1. The distribution of nonsynonymous substitutions was biphasic, with most of the adaptation of env variable regions occurring in the first three passages. This phase, in which the symptom-free period fell to 4 months, was followed by a plateau phase of apparently reduced adaptation. Analysis of codon usage revealed decreased codon redundancy in the variable regions. Overall, the results suggested a biphasic pattern of adaptation and evolution, with extremely rapid selection in the first three passages followed by an equilibrium or stabilization of the variation between env clones at different time points in passages four to six.     

Study of factors affecting the determination of total plasma 7-fluorobenzo-2-oxa-1,3-diazole-4-sulfonate (SBD)–thiol derivatives by liquid chromatography

A detailed investigation of the factors affecting the determination of total plasma 7-fluorobenzo-2-oxa-1,3-diazole-4-sulfonate (SBD)–thiol derivatives (i.e. cysteine, homocysteine and cysteinylglycine) is described. Essentially, this assay entails extracting specific thiols by plasma disulphide bond reduction, protein precipitation, sulphydryl compound derivatization with the thiol-specific fluorogenic reagent ammonium 7-fluorobenzo-2-oxa-1,3-diazole-4-sulphonate (SBD-F), and subsequent separation with isocratic reversed-phase high-performance liquid chromatography. By improving the reliability of several analytical parameters (composition of the mobile phase, pretreatment of the sample using different reducing and protein precipitation agents, and optimization of the derivatization of thiols with SBD-F), a number of critical issues can be identified and solved.     

Influence of age and sex on the acute toxicity of two steroid anesthetics in rats]

During the newborn period, there is a hight increase of the acute toxicity of two steroid anaesthetics (Hydroxydione, Althesin) given by intraperitoneal route on the rat as also an influence of hormonal conditions.     

Hepatitis B virus (HBV)-specific cytotoxic T-cell (CTL) response in humans: characterization of HLA class II-restricted CTLs that recognize endogenously synthesized HBV envelope antigens.

In this study, we show that CD4+, hepatitis B virus (HBV) envelope-specific T-cell clones produced by stimulation with a particulate antigen preparation are able to recognize and kill not only autologous antigen-presenting cells incubated with exogenous HBV envelope antigens but also autologous HLA class II-positive cells expressing endogenously synthesized HBV envelope antigens following infection with recombinant vaccinia viruses or transfection with recombinant Epstein-Barr virus expression vectors. Experiments with lysosomotropic agents and brefeldin A suggest that the endosomal compartment is likely involved in the processing of endogenously synthesized viral proteins for recognition by CD4+ T cells. Our study indicates that HBV envelope-specific, HLA class II-restricted CD4+ cytotoxic T lymphocytes can potentially participate in the immune clearance of HBV-infected cells and the pathogenesis of hepatocellular injury in hepatitis B.     

Vigorous exercise acutely changes platelet and B-lymphocyte CD39 expression.

CD39/ATP diphosphohydrolase is expressed on B lymphocytes, cytotoxic T lymphocytes, monocytes, platelets, and endothelial cells, and it has a critical role in the inhibition of platelet responsiveness. To determine whether strenuous exercise could acutely change expression of CD39 in platelets and lymphocytes, eight healthy sedentary men, 34 yr old (SD 7), and eight physically active men, 34 yr old (SD 6), performed graded upright cycle ergometry to volitional exhaustion. Blood samples collected both at baseline and after exercise test were employed to measure CD39 expression in platelets and lymphocytes. The percentage of circulating platelet-platelet aggregates, the "in vitro" ADP and collagen-induced platelet aggregation, and the expression of both platelet glycoprotein IIb-IIIa (PAC-1) and P-selectin (CD62) were also considered markers of platelet activation. After strenuous exercise, all subjects demonstrated significant platelet activation as judged by the increased percentage of platelet-platelet aggregates. The in vitro ADP-induced platelet aggregation and the expression of CD62P on ADP-stimulated platelets significantly increased in sedentary but not in active subjects. After exercise, all of the subjects showed a significant reduction of CD39 expression in platelet [sedentary: from 2.2 (SD 0.8) to 1.1% (SD 0.8), P = 0.008; active: from 0.6 (SD 0.2) to 0.35% (SD 0.1), P = 0.009] and an increase of CD39 expression in B lymphocytes [sedentary: from 47 (SD 13) to 60% (SD 11), P = 0.0039; active: from 46 (SD 11) to 59% (SD 11), P = 0.0038]. Taken together, these findings confirm the critical role of this ADPase in inhibition of platelet responsiveness, also suggesting a possible role of B lymphocytes in thromboregulation mechanism.     

Engineering surfaces for bioconjugation: developing strategies and quantifying the extent of the reactions

This study presents two-step and multistep reactions for modifying the surface of plasma-functionalized poly(tetrafluoroethylene) (PTFE) surfaces for subsequent conjugation of biologically relevant molecules. First, PTFE films were treated by a radiofrequency glow discharge (RFGD) ammonia plasma to introduce amino groups on the fluoropolymer surface. This plasma treatment is well optimized and allows the incorporation of a relative surface concentration of approximately 2-3.5% of amino groups, as assessed by chemical derivatization followed by X-ray photoelectron spectroscopy (XPS). In a second step, these amino groups were further reacted with various chemical reagents to provide the surface with chemical functionalities such as maleimides, carboxylic acids, acetals, aldehydes, and thiols, that could be used later on to conjugate a wide variety of biologically relevant molecules such as proteins, DNA, drugs, etc. In the present study, glutaric and cis-aconitic anhydrides were evaluated for their capability to provide carboxylic functions to the PTFE plasma-treated surface. Bromoacetaldehyde diethylacetal was reacted with the aminated PTFE surface, providing a diethylacetal function, which is a latent form of aldehyde functionality. Reactions with cross-linkers such as sulfo-succinimidyl derivatives (sulfo-SMCC, sulfo-SMPB) were evaluated to provide a highly reactive maleimide function suitable for further chemical reactions with thiolated molecules. Traut reagent (2-iminothiolane) was also conjugated to introduce a thiol group onto the fluoropolymer surface. PTFE-modified surfaces were analyzed by XPS with a particular attention to quantify the extent of the reactions that occurred on the polymer. Finally, surface immobilization of fibronectin performed using either glutaric anhydride or sulfo-SMPB activators demonstrated the importance of selecting the appropriate conjugation strategy to retain the protein biological activity.     

An AIF orthologue regulates apoptosis in yeast

Apoptosis-inducing factor (AIF), a key regulator of cell death, is essential for normal mammalian development and participates in pathological apoptosis. The proapoptotic nature of AIF and its mode of action are controversial. Here, we show that the yeast AIF homologue Ynr074cp controls yeast apoptosis. Similar to mammalian AIF, Ynr074cp is located in mitochondria and translocates to the nucleus of yeast cells in response to apoptotic stimuli. Purified Ynr074cp degrades yeast nuclei and plasmid DNA. YNR074C disruption rescues yeast cells from oxygen stress and delays age-induced apoptosis. Conversely, overexpression of Ynr074cp strongly stimulates apoptotic cell death induced by hydrogen peroxide and this effect is attenuated by disruption of cyclophilin A or the yeast caspase YCA1. We conclude that Ynr074cp is a cell death effector in yeast and rename it AIF-1 (Aif1p, gene AIF1).     

Design of HIV-1-PR inhibitors that do not create resistance: blocking the folding of single monomers

The main problems found in designing drugs are those of optimizing the drug-target interaction and of avoiding the insurgence of resistance. We suggest a scheme for the design of inhibitors that can be used as leads for the development of a drug and that do not face either of these problems, and then apply it to the case of HIV-1-PR. It is based on the knowledge that the folding of single-domain proteins, such as each of the monomers forming the HIV-1-PR homodimer, is controlled by local elementary structures (LES), stabilized by local contacts among hydrophobic, strongly interacting, and highly conserved amino acids that play a central role in the folding process. Because LES have evolved over many generations to recognize and strongly interact with each other so as to make the protein fold fast and avoid aggregation with other proteins, highly specific (and thus little toxic) as well as effective folding-inhibitor molecules suggest themselves: short peptides (or eventually their mimetic molecules) displaying the same amino acid sequence of that of LES (p-LES). Aside from being specific and efficient, these inhibitors are expected not to induce resistance; in fact, mutations in HIV-1-PR that successfully avoid the action of p-LES imply the destabilization of one or more LES and thus should lead to protein denaturation. Making use of Monte Carlo simulations, we first identify the LES of the HIV-1-PR and then show that the corresponding p-LES peptides act as effective inhibitors of the folding of the protease.