Induction of ATP depletion, intramembrane particle aggregation and exposure of membrane phospholipids in chicken erythrocytes by local anesthetics and tranquilizers

Incubation of chicken erythrocytes with 1 mM tetracaine, 10 mM lidocaine and 0.24–0.48 mM chlorpromazine significantly reduced the ATP content of the cells, while procaine even at concentrations as high as 10 mM had only a slight effect. When chlorpromazine was used, it was found that the final level of the ATP was dependent on the drug concentration, which at 0.48 mM depletes the cells to about 10% of the initial ATP content. The ATP depletion of chicken erythrocytes was accompanied by dephosphorylation of certain membrane proteins which were identified by acrylamide gel electrophoresis as an 180 000 dalton protein band and peptides with molecular weight of 60 000–100 000. Treatment of chicken and rat erythrocytes with 0.5 mM tetracaine and 1 mM lidocaine or with 0.48 mM chlorpromazine induced significant aggregation of intramembrane particles as revealed by the freeze-etching technique. Procaine (10 mM) had no effect. Incubation of chicken erythrocytes with the above-mentioned drugs induced also exposure of the masked membrane phospholipids to the action of phospholipase-C (Bacillus cereus) and to phospholipase A₂ (bee venom). Negligible amounts of phospholipids were hydrolyzed in the untreated cells, while about 40% of the membrane phosphatidylethanolamine and 50% of the phosphatidylcholine were hydrolyzed by phospholipase A₂ in chicken erythrocytes treated with 0.48 mM chlorpromazine.Treatment of chicken and rat erythrocytes with 0.48 mM chlorpromazine resulted also in an increase in the amount of the phospholipid fraction which could be extracted by dry ether. About 41% and 60% of phospholipids were respectively, as compared to 25% and 35% of phospholipids extracted from the same untreated cells.     

Phosphorylation of chlamydomonas reinhardi chloroplast membrane proteins in vivo and in vitro

Phosphorylation of thylakoid membrane proteins in the chloroplast of wild-type and mutant strains of Chlamydomonas reinhardi has been studied in vivo and in vitro. Intact cells or purified membranes were labeled with [32P]orthophosphate or [gamma-32P]ATP, respectively, and the presence of phosphorylated polypeptides was detected by autoradiography after membrane fractionation by SDS PAGE. The 32P was esterified to serine and threonine residues. At least six polypeptides were phosphorylated in vitro and in vivo, and corresponded to components of the photosystem II complex contributing to the formation of the light-harvesting-chlorophyll (LHC) a,b-protein complex, the DCMU binding site (32-35 kdaltons), and the reaction center (26 kdaltons). In agreement with previous reports (Alfonzo, et al., 1979, Plant Physiol., 65:730-734; and Bennett, 1979, FEBS (Fed. Eur. Biochem. Soc.) Lett., 103:342-344), the membrane-bound protein kinase was markedly stimulated by light in vitro via a mechanism requiring photosystem II activity. Phosphorylation of thylakoid membrane polypeptides in vivo was, however, completely independent of illumination. Similar amounts of phosphate were incorporated into the photosynthetic membranes of cells incubated in the dark, in white light with or without 3-(3,4- dichlorophenyl-1,1-dimethyl urea (DCMU), or in red or far-red light. Different turnovers of the phosphate were observed in the light and dark, and a phosphoprotein phosphatase involved in this turnover process was also associated with the membrane. Comparison of the amount of esterified phosphate per protein in vivo and the maximum incorporation in isolated membranes revealed that only a small fraction of the available sites could be phosphorylated in vitro. In contrast to the DCMU binding site, the LHC and 26-kdalton polypeptide were not phosphorylated in vivo when the reaction center II polypeptides of 44- 54 kdaltons were missing. The finding that all the phosphoproteins appear to be components of the photosystem II complex and are only partially dephosphorylated in vivo suggests strongly that protein phosphorylation might play an important role in the maintenance of the organizational integrity of this complex. The observation that the LHC is not phosphorylated in the absence of the reaction center lends support to this idea.     

Functional Organization of the Chlorophyll-Containing Complexes of Chlamydomonas reinhardi: A Study of Their Formation and Interconnection with Reaction Centers in the Greening Process of the y-1 Mutant

The stepwise synthesis and assembly of photosynthetic membrane components in the y-1 mutant of Chlamydomonas reinhardi have been previously demonstrated (Ohad 1975 In Membrane Biogenesis, Mitochondria, Chloroplasts and Bacteria, Plenum, pp 279-350). This experimental system was used here in order to investigate the process of formation and interconnection of the energy collecting chlorophylls with the reaction centers of both photosystems I and II. The following measurements were carried out: photosynthetic electron flow at various light intensities, including parts or the entire electron transfer chain; analysis of the kinetics of fluorescence emission at room temperature and fluorescence emission spectra at 77 K, and electrophoretic separation of membrane polypeptides and chlorophyll protein complexes. Based on the data obtained it is concluded that: (a) each photosystem (PSI and PSII) contains, in addition to the reaction center, an interconnecting antenna and a main or light harvesting antenna complex; (b) the formation of the light harvesting complex, interconnecting antenna, and reaction centers for each photosystem can occur independently. (c) the interconnecting antennae link the light harvesting complexes with the respective reaction centers. In their absence, energy transfer between the light harvesting chlorophylls and the reaction centers is inefficient. The formation of the interconnecting antennae and efficient assembly of photosystem components occur simultaneously with the de novo synthesis of chlorophyll and at least three polypeptides, one translated in the cytoplasm and two translated in the chloroplast. The synthesis of these polypeptides was found to be light dependent.     

Leibnizian organisms,nested individuals,and units of selection

Summary Leibniz developed a new notion of individuality, according to which individuals are nested one within another, thereby abandoning the Aristotelian formula at the heart of substantialist metaphysics, ‘one body, one substance’. On this model, the level of individuality is determined by the degree of activity, and partly defined by its relations with other individuals. In this article, we show the importance of this new notion of individuality for some persisting questions in theoretical biology. Many evolutionary theorists presuppose a model of individuality that will eventually reduce to spatiotemporal mechanisms, and some still look for an exclusive level or function to determine a unit of selection. In recent years, a number of alternatives to these exclusive approaches have emereged, and no consensus can be foreseen. It is for this reason that we propose the model of nested individuals. This model supports pluralistic multi-level selection and rejects an exclusive level or function for a unit of selection. Since activity is essential to the unity of an individual, this model focuses on integrating processes of interaction and replication instead of choosing between them. In addition, the model of nested individuals may also be seen as a distinct perspective among the various alternative models for the unit of selection. This model stresses activity and pluralism: it accepts simultaneuous co-existence of individuals at different levels, nested one within the other. Our aim in this article is to show now a chapter of the history of metaphysics may be fruitfully brought to bear on the current debate over the unit of selection in evolutionary biology.     

Homologous adaptation to oxidative stress induced by the photosensitized Pd-bacteriochlorophyll derivative (WST11) in cultured endothelial cells

Various forms of cellular stress induce adaptive responses through poorly understood mechanisms. In maintaining homeostasis, endothelial cells respond and adapt to changes in oxidative stress that prevail in the circulation. Endothelial cells are also the target of many oxidative stress-based vascular therapies. The objectives of this study were to determine whether endothelial cells adapt to oxidative stress induced upon the photosensitization of WST11 (a water-soluble Pd-bacteriochlorophyll derivative being developed as a photodynamic agent) and to study possible cellular mechanisms involved. The hallmark of WST11-based photodynamic therapy is the in situ generation of cytotoxic reactive oxygen species causing vascular shutdown, hypoxia, and tumor eradication. Here we demonstrated that photodynamic therapy also induces adaptive responses and tolerance following a sublethal preconditioning of endothelial cells with the same (homologous) or different (heterologous) stressor. A link among p38 MAPK activity, expression of hsp70 and hsp27, and homologous adaptation to reactive oxygen species induced by photosensitized WST11 was established. In addition to characterization of some key proteins involved, our observations provide a beneficial new working tool for the studies of mechanisms involved in oxidative stress and adaptation using light-controlled photosensitization.     

<Emphasis Type="Italic">CHX10</Emphasis> mutations cause non-syndromic microphthalmia/anophthalmia in Arab and Jewish kindreds

Microphthalmia/anophthalmia is a clinically heterogeneous disorder of eye formation, ranging from small size of a single eye to complete bilateral absence of ocular tissues. The genetic defect underlying isolated autosomal recessive microphthalmia/anophthalmia is yet unclear. We studied four families (two of Arab origin, one of Bedouin origin, and one of Persian-Jewish origin) with autosomal recessive microphthalmia/anophthalmia and no associated eye anomalies, and one Syrian–Jewish family with associated colobomas. Assuming a founder effect in each of the families, we performed homozygosity mapping using polymorphic markers adjacent to human homologues of genes known to be associated with eye absence in various species, namely EYA1, EYA2, EYA3, SIX4, SIX6, PAX6 and CHX10. No association was found with EYA1, EYA2, EYA3, SIX6 or PAX6. In two families, linkage analysis was consistent with possible association with SIX4, but no mutations were found in the coding region of the gene or its flanking intron sequences. In three of the five families, linkage analysis followed by sequencing demonstrated that affected individuals in each family were homozygous for a different CHX10 aberration: a mutation in the CVC domain and a deletion of the homeobox domain were found in two Arab families, and a mutation in the donor-acceptor site in the first intron in the Syrian-Jewish family. There was phenotypic variation between families having different mutations, but no significant phenotypic variation within each family. It has been previously shown that mutations in a particular nucleotide in CHX10 are associated with an autosomal recessive syndrome of microphthalmia/anophthalmia with iris colobomas and cataracts in two families. We now show that different mutations in other domains of the same gene underlie isolated microphthalmia/anophthalmia.     

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Structural basis for the thermostability of ferredoxin from the cyanobacterium Mastigocladus laminosus

Plant-type ferredoxins (Fds) carry a single [2Fe-2S] cluster and serve as electron acceptors of photosystem I (PSI). The ferredoxin from the thermophilic cyanobacterium Mastigocladus laminosus displays optimal activity at 65 degrees C. In order to reveal the molecular factors that confer thermostability, the crystal structure of M.laminosus Fd (mFd) was determined to 1.25 A resolution and subsequently analyzed in comparison with four similar plant-type mesophilic ferredoxins. The topologies of the plant-type ferredoxins are similar, yet two structural determinants were identified that may account for differences in thermostability, a salt bridge network in the C-terminal region, and the flexible L1,2 loop that increases hydrophobic accessible surface area. These conclusions were verified by three mutations, i.e. substitution of L1,2 into a rigid beta-turn ((Delta)L1,2) and two point mutations (E90S and E96S) that disrupt the salt bridge network at the C-terminal region. All three mutants have shown reduced electron transfer (ET) capabilities and [2Fe-2S] stability at high temperatures in comparison to the wild-type mFd. The results have also provided new insights into the involvement of the L1,2 loop in the Fd interactions with its electron donor, the PSI complex.     

Predicting Disease Risk Using Bootstrap Ranking and Classification Algorithms

Genome-wide association studies (GWAS) are widely used to search for genetic loci that underlie human disease. Another goal is to predict disease risk for different individuals given their genetic sequence. Such predictions could either be used as a “black box” in order to promote changes in life-style and screening for early diagnosis, or as a model that can be studied to better understand the mechanism of the disease. Current methods for risk prediction typically rank single nucleotide polymorphisms (SNPs) by the p-value of their association with the disease, and use the top-associated SNPs as input to a classification algorithm. However, the predictive power of such methods is relatively poor. To improve the predictive power, we devised BootRank, which uses bootstrapping in order to obtain a robust prioritization of SNPs for use in predictive models. We show that BootRank improves the ability to predict disease risk of unseen individuals in the Wellcome Trust Case Control Consortium (WTCCC) data and results in a more robust set of SNPs and a larger number of enriched pathways being associated with the different diseases. Finally, we show that combining BootRank with seven different classification algorithms improves performance compared to previous studies that used the WTCCC data. Notably, diseases for which BootRank results in the largest improvements were recently shown to have more heritability than previously thought, likely due to contributions from variants with low minimum allele frequency (MAF), suggesting that BootRank can be beneficial in cases where SNPs affecting the disease are poorly tagged or have low MAF. Overall, our results show that improving disease risk prediction from genotypic information may be a tangible goal, with potential implications for personalized disease screening and treatment.     

Diet-induced obesity in rats leads to a decrease in sperm motility

Background  

Obesity is rapidly becoming a worldwide epidemic that affects children and adults. Some studies have shown a relationship between obesity and infertility, but until now it remains controversial. Thus, the aim of the present study was to investigate the effect of high-fat diet-induced obesity on male reproductive parameters.