Cannibalism as a life boat mechanism

Under certain conditions a cannibalistic population can survive when food for the adults is too scarce to support a non-cannibalistic population. Cannibalism can have this lifeboat effect if (i) the juveniles feed on a resource inaccessible to the adults; and (ii) the adults are cannibalistic and thus incorporate indirectly the inaccessible resource. Using a simple model we conclude that the mechanism works when, at low population densities, the average yield, in terms of new offspring, due to the energy provided by one cannibalized juvenile is larger than one.     

Cardiolipin, a lipid found in mitochondria, hydrogenosomes and bacteria was not detected in Giardia lamblia

Giardia lamblia is a protozoan parasite with many characteristics common among eukaryotic cells, but lacking other features found in most eukaryotes. Cardiolipin is a phospholipid located exclusively in energy transducing membranes and it was identified in mitochondria, bacteria, hydrogenosomes and chloroplasts. In eukaryotes, cardiolipin is the only lipid that is synthesized in the mitochondria. Biochemical procedures (TLC, HPLC) and fluorescent tools (NAO) were applied in order to search for cardiolipin in G. lamblia. In addition, BLAST searches were used to find homologs of enzymes that participate in the cardiolipin synthesis. Cardiolipin synthase was searched in the Giardia genome, using Saccharomyces cerevisiae and Mycoplasma penetrans sequences as bait. However, a good match to G. lamblia related proteins was not found. Here we show that mitosomes of G. lamblia apparently do not contain cardiolipin, which raises the discussion for its endosymbiotic origin and for the previous proposal that Giardia mitosomes are modified mitochondria.     

The Genetic Legacy of Religious Diversity and Intolerance: Paternal Lineages of Christians, Jews, and Muslims in the Iberian Peninsula

Most studies of European genetic diversity have focused on large-scale variation and interpretations based on events in prehistory, but migrations and invasions in historical times could also have had profound effects on the genetic landscape. The Iberian Peninsula provides a suitable region for examination of the demographic impact of such recent events, because its complex recent history has involved the long-term residence of two very different populations with distinct geographical origins and their own particular cultural and religious characteristics—North African Muslims and Sephardic Jews. To address this issue, we analyzed Y chromosome haplotypes, which provide the necessary phylogeographic resolution, in 1140 males from the Iberian Peninsula and Balearic Islands. Admixture analysis based on binary and Y-STR haplotypes indicates a high mean proportion of ancestry from North African (10.6%) and Sephardic Jewish (19.8%) sources. Despite alternative possible sources for lineages ascribed a Sephardic Jewish origin, these proportions attest to a high level of religious conversion (whether voluntary or enforced), driven by historical episodes of social and religious intolerance, that ultimately led to the integration of descendants. In agreement with the historical record, analysis of haplotype sharing and diversity within specific haplogroups suggests that the Sephardic Jewish component is the more ancient. The geographical distribution of North African ancestry in the peninsula does not reflect the initial colonization and subsequent withdrawal and is likely to result from later enforced population movement—more marked in some regions than in others—plus the effects of genetic drift.     

Five pseudoknots are present at the 204 nucleotides long 3'' noncoding region of tobacco mosaic virus RNA.

The 104 nucleotides long 3' terminal region of TMV RNA was shown previously to contain two pseudoknotted structures (Rietveld et al. (1984), EMBO J. 3, 2613-2619). We here present evidence for the occurrence, within the 204 nucleotides long 3' noncoding region, of another highly structured domain located immediately adjacent to the tRNA-like structure of 95 nucleotides (Joshi et al. (1985) Nucleic Acids Res. 13, 347-354). A model for the three-dimensional folding of this region, containing three more pseudoknots, is proposed on the basis of chemical modification and enzymatic digestion. The existence of these three consecutive pseudoknots was supported by sequence comparisons with the RNA from the related tobamoviruses TMV-L, CcTMV and CGMMV. Coaxial stacking of the six double helical segments involved gives rise to the formation of a 25 basepair long quasi-continuous double helix. The results show that the three-dimensional folding of the 3' non-translated region of tobamoviral RNAs is largely maintained by the formation of five pseudoknots. The organisation of this region in the RNA of the tobamovirus CcTMV suggests that recombinational events among aminoacylatable plant viral RNAs have to be considered.     

Differential phosphorylation of band 3 and glycophorin in intact and extracted erythrocyte membranes

This report presents an analysis of the phosphorylation of human and rabbit erythrocyte membrane proteins which migrate in NaDodSO₄-polyacrylamide gels in the area of the Coomassie Blue-stained proteins generally known as band 3. The phosphorylation of these proteins is of interest as band 3 has been implicated in transport processes. This study shows that there are at least three distinct phosphoproteins associated with the band 3 region of human erythrocyte membranes. These are band 2.9, the major band 3, and PAS-1. The phosphorylation of these proteins is differentially catalyzed by solubilized membrane and cytoplasmic cyclic AMP-dependent and -independent erythrocyte protein kinases. Band 2.9 is present and phosphorylated in unfractionated human and rabbit erythrocyte ghosts but not in NaI- or dimethylmaleic anhydride (DMMA)-extracted membranes. These latter membrane preparations are enriched in band 3 and in sialoglycoproteins. The NaI-extracted ghosts contain residual protein kinase activity which can catalyze the autophosphorylation of band 3 whereas the DMMA-extracted ghosts are usually devoid of any kinase activity. However, both NaI- and DMMA-extracted ghosts, as well as Triton X-100 extracts of the DMMA-extracted ghosts, can be phosphorylated by various erythrocyte protein kinases. The kinases which preferentially phosphorylate the major band 3 protein are inactive towards PAS-1 while the kinases active towards PAS-1 are less active towards band 3. The band 3 protein in the DMMA-extracted ghosts can be cross-linked with the Cu²⁺ -σ-phenanthroline complex. The cross-linking of band 3 does not affect its capacity to serve as a phosphoryl acceptor nor does phosphorylation affect the capacity of band 3 to form cross-links. In addition to band 2.9, the major band 3 and PAS-1, another minor protein component appears to be present in the band 3 region in human erythrocyte membranes. This protein is specifically phosphorylated by the cyclic AMP-dependent protein kinases isolated from the cytoplasm of rabbit erythrocytes. The rabbit erythrocyte membranes lack PAS-1 and the cyclic AMP-dependent protein kinase substrate.     

Receptor-mediated delivery of engineered nucleases for genome modification

Engineered nucleases, which incise the genome at predetermined sites, have a number of laboratory and clinical applications. There is, however, a need for better methods for controlled intracellular delivery of nucleases. Here, we demonstrate a method for ligand-mediated delivery of zinc finger nucleases (ZFN) proteins using transferrin receptor-mediated endocytosis. Uptake is rapid and efficient in established mammalian cell lines and in primary cells, including mouse and human hematopoietic stem-progenitor cell populations. In contrast to cDNA expression, ZFN protein levels decline rapidly following internalization, affording better temporal control of nuclease activity. We show that transferrin-mediated ZFN uptake leads to site-specific in situ cleavage of the target locus. Additionally, despite the much shorter duration of ZFN activity, the efficiency of gene correction approaches that seen with cDNA-mediated expression. The approach is flexible and general, with the potential for extension to other targeting ligands and nuclease architectures.     

Characterization of an ectonucleoside triphosphate diphosphohydrolase 1 activity in alkaline phosphatase-depleted rat osseous plate membranes: possible functional involvement in the calcification process

An ectonucleoside triphosphate diphosphohydrolase 1 (NTPDase1) activity present in alkaline phosphatase-depleted rat osseous plate membranes, obtained 14 days after implantation of demineralized bone particles in the subcutaneous tissue of Wistar rats, was characterized. At pH 7.5, NTPDase1 hydrolyzed nucleotide triphosphates at rates 2.4-fold higher than those of nucleotide diphosphates, while the hydrolysis of nucleotide monophosphates and non-nucleotide phosphates was negligible. NTPDase 1 hydrolyzed ATP and ADP following Michaelis-Menten kinetics with V=1278.7+/-38.4 nmol Pi/min/mg and K(M)=83.3+/-2.5 microM and V=473.9+/-18.9 nmol Pi/min/mg and K(M)=150.6+/-6.0 microM, respectively, but in the absence of magnesium and calcium ions, ATP or ADP hydrolysis was negligible. The stimulation of the NTPDase1 by calcium (V=1084.7+/-32.5 nmol Pi/min/mg; and K(M)=377.8+/-11.3 microM) and magnesium (V=1367.2+/-41.0 nmol Pi/min/mg and K(M)=595.3+/-17.8 microM) ions suggested that each ion could replace the other during the catalytic cycle of the enzyme. Oligomycin, ouabain, bafilomycin A(1), theophylline, thapsigargin, ethacrynic acid, P(1),P(5)-(adenosine-5')-pentaphosphate and omeprazole had negligible effects on the hydrolysis of ATP and ADP by NTPDase1. However, suramin and sodium azide were effective inhibitors of ATP and ADP hydrolysis.To our knowledge this is the first report suggesting the presence of NTPDase1 in rat osseous plate membranes. Considering that the ectonucleoside triphosphate diphosphohydrolase family of enzymes participates in many regulatory functions, such as response to hormones, growth control, and cell differentiation, the present observations raise interesting questions about the participation of this activity in the calcification process.     

Y-chromosomal diversity in Europe is clinal and influenced primarily by geography, rather than by language

Clinal patterns of autosomal genetic diversity within Europe have been interpreted in previous studies in terms of a Neolithic demic diffusion model for the spread of agriculture; in contrast, studies using mtDNA have traced many founding lineages to the Paleolithic and have not shown strongly clinal variation. We have used 11 human Y-chromosomal biallelic polymorphisms, defining 10 haplogroups, to analyze a sample of 3,616 Y chromosomes belonging to 47 European and circum-European populations. Patterns of geographic differentiation are highly nonrandom, and, when they are assessed using spatial autocorrelation analysis, they show significant clines for five of six haplogroups analyzed. Clines for two haplogroups, representing 45% of the chromosomes, are continentwide and consistent with the demic diffusion hypothesis. Clines for three other haplogroups each have different foci and are more regionally restricted and are likely to reflect distinct population movements, including one from north of the Black Sea. Principal-components analysis suggests that populations are related primarily on the basis of geography, rather than on the basis of linguistic affinity. This is confirmed in Mantel tests, which show a strong and highly significant partial correlation between genetics and geography but a low, nonsignificant partial correlation between genetics and language. Genetic-barrier analysis also indicates the primacy of geography in the shaping of patterns of variation. These patterns retain a strong signal of expansion from the Near East but also suggest that the demographic history of Europe has been complex and influenced by other major population movements, as well as by linguistic and geographic heterogeneities and the effects of drift.     

Structural plasticity of dendritic spines

Dendritic spines are small mushroom-like protrusions arising from neurons where most excitatory synapses reside. Their peculiar shape suggests that spines can serve as an autonomous postsynaptic compartment that isolates chemical and electrical signaling. How neuronal activity modifies the morphology of the spine and how these modifications affect synaptic transmission and plasticity are intriguing issues. Indeed, the induction of long-term potentiation (LTP) or depression (LTD) is associated with the enlargement or shrinkage of the spine, respectively. This structural plasticity is mainly controlled by actin filaments, the principal cytoskeletal component of the spine. Here we review the pioneering microscopic studies examining the structural plasticity of spines and propose how changes in actin treadmilling might regulate spine morphology.