Dalmatian: spotting the difference in cohesin protectors

The cohesin complex prevents separation of chromosomes following their duplication until the appropriate time during cell division. In vertebrates, establishment and maintenance of cohesin‐dependent linkages depend on two distinct proteins, sororin and shugoshin. New findings published in The EMBO Journal show that in Drosophila, the function of both of these cohesin regulators is carried out by a single hybrid protein, Dalmatian.     

Dendritic cells present lytic antigens and maintain function throughout persistent gamma-herpesvirus infection

The activation and maintenance of Ag-specific CD8(+) T cells is central to the long-term control of persistent infections. These killer T cells act to continuously scan and remove reservoirs of pathogen that have eluded the acute immune response. Acutely cleared viral infections depend almost exclusively on dendritic cells (DC) to present Ags to, and to activate, the CD8(+) T cell response. Paradoxically, persistent pathogens often infect professional APCs such as DC, in addition to infecting a broad range of nonprofessional APC, raising the possibility that many cell types could present viral Ags and activate T cells. We addressed whether in persistent viral infection with murine gammaherpesviruses, DC or non-DC, such as B cells and macrophages, were required to maintain the continued activation of Ag-specific CD8(+) T cells. We found that presentation of the surrogate Ag, OVA, expressed under a lytic promoter to CD8(+) T cells during persistent infection was largely restricted to DC, with little contribution from other lymphoid resident cells, such as B cells. This is despite the fact that B cells harbor a very large reservoir of latent virus. Our results support that, during persistent viral infection, continual presentation of lytic Ags by DC leads to T cell activation critical for maintaining CD8(+) T cells capable of limiting persistent viral infection.     

Feedback inhibition of pantothenate kinase regulates pantothenol uptake by the malaria parasite

To survive, the human malaria parasite Plasmodium falciparum must acquire pantothenate (vitamin B5) from the external medium. Pantothenol (provitamin B5) inhibits parasite growth by competing with pantothenate for pantothenate kinase, the first enzyme in the coenzyme A biosynthesis pathway. In this study we investigated pantothenol uptake by P. falciparum and in doing so gained insights into the regulation of the parasite's coenzyme A biosynthesis pathway. Pantothenol was shown to enter P. falciparum-infected erythrocytes via two routes, the furosemide-inhibited "new permeation pathways" induced by the parasite in the infected erythrocyte membrane (the sole access route for pantothenate) and a second, furosemide-insensitive pathway. Having entered the erythrocyte, pantothenol is taken up by the intracellular parasite via a mechanism showing functional characteristics distinct from those of the parasite's pantothenate uptake mechanism. On reaching the parasite cytosol, pantothenol is phosphorylated and thereby trapped by pantothenate kinase, shown here to be under feedback inhibition control by coenzyme A. Furosemide reduced this inherent feedback inhibition by competing with coenzyme A for binding to pantothenate kinase, thereby increasing pantothenol uptake.     

Association of body iron stores with low molecular weight iron and oxidant damage of human atherosclerotic plaques

The association between iron, an oxidant catalyst, and atherosclerosis is controversial. In particular, it is unknown whether: (1) stored iron, namely serum ferritin, is correlated with catalytic iron and oxidant damage of human atherosclerotic plaques; (2) catalytic iron is related to oxidative injury within such plaques; (3) plaque oxidant burden is associated with the severity of atherosclerosis. Thus, we assessed low molecular weight iron (LMWI), which represents the metal catalytically active form, together with fluorescent damage products of lipid peroxidation (FDPL) and lipid hydroperoxides (LOOH), in 38 atherosclerotic plaques surgically removed from 38 patients who had undergone selective carotid endarterectomy. In each patient, the levels of serum ferritin were measured and correlated with those of plaque LMWI and lipoperoxides by the Spearman rank correlation test with Spearman rank correlation coefficient (r(S)) calculation. Moreover, in patients selected from the same study population, we compared plaque analyte levels between two groups with different severity of atherosclerotic carotid stenosis, i.e., <90% (group A, n = 25) or > or =90% (group B, n = 13), and between another two groups without (group C, n = 27) and with (group D, n = 11) associated contralateral carotid stenosis > or =50%, indicative of "extensive" and more severe atherosclerotic disease. In group A patients, serum ferritin was directly and significantly correlated with plaque LMWI (r(S) = 0.46, P < 0.025) and FDPL (r(S) = 0.58, P < 0.005), while its correlation with plaque LOOH, albeit direct, did not attain statistical significance. Moreover, a direct and significant relationship was evident between the plaque content of LMWI and that of both FDPL (r(S) = 0.61, P < 0.0025) and LOOH (r(S) = 0.51, P < 0.025), suggesting a prooxidant role of catalytic iron within human atherosclerotic plaques. Considering the 13 patients of group B, a positive and significant correlation was observed between the levels of serum ferritin and those of plaque LMWI (r(S) = 0.83, P < 0.0001); on the other hand, serum ferritin, as well as plaque LMWI, showed no significant correlation with either plaque FDPL or LOOH, conceivably reflecting the small number of patients belonging to group B. Finally, plaque LMWI, FDPL, and LOOH content was significantly higher in group B than in group A, and in group D than in group C. These data suggest a role for catalytic iron in atherosclerotic plaque oxidation and in the severity of atherosclerosis, which appears indeed associated with plaque oxidant burden.     

Identification of cytoplasmic and membrane-associated complexes in human embryonic stem cells using blue native PAGE

Human embryonic stem cells (hESCs) have great potential for use in developmental biology studies, functional genomics applications, drug screening, and regenerative medicine. A detailed understanding of the molecular mechanisms that are responsible for maintaining the undifferentiated and pluripotent nature of hESCs is essential for their effective therapeutic application. It has become evident that many complex cellular processes are carried out by assemblies of protein molecules (protein complexes). Blue native polyacrylamide gel electrophoresis (BN-PAGE) has been used to separate protein complexes from whole cell lysates. Using BN-PAGE, we resolved cytoplasmic and membrane-associated complexes from hESCs and characterised their composition, stoichiometry, and dynamics by denaturing SDS-PAGE. The reliability of the fractionation was examined by western blot analysis of membrane and cytosolic markers. MALDI TOF/TOF mass spectrometry identified 119 cytosolic and 69 membrane proteins from the BN-PAGE proteome maps. Potential protein complexes were validated by computational prediction of possible protein-protein interactions using the Search Tool for the Retrieval of Interacting Genes/Proteins (STRING) database. Based on BN-PAGE gels and validation by databases, 82 heteromultimeric and 47 homomultimeric protein complexes have been found in hESCs. Resolving some of the protein complexes provided insight into the function of previously uncharacterised complexes in hESCs.     

Age as a Criterion for Setting Priorities in Health Care? A Survey of the German Public View

Although the German health care system has budget constraints similar to many other countries worldwide, a discussion on prioritization has not gained the attention of the public yet. To probe the acceptance of priority setting in medicine, a quantitative survey representative for the German public (n = 2031) was conducted. Here we focus on the results for age, a highly disputed criterion for prioritizing medical services. This criterion was investigated using different types of questionnaire items, from abstract age-related questions to health care scenarios, and discrete choice settings, all performed within the same sample. Several explanatory variables were included to account for differences in preference; in particular, interviewee''s own age but also his or her sex, socioeconomic status, and health status. There is little evidence that the German public accepts age as a criterion to prioritize health care services.     

Über die einwirkung von Röntgenstrahlen auf Amphibienlarven

Ohne Zusammenfassung Mit 22 Textabbildungen.     

Ten years of predictions ... and counting

The CASP experiment has been run every other year since 1994. Its objective is to subject the available structure prediction methods to a blind test. This is a short report of the highlights of its last edition. 'Men who wish to know about the world must learn about it in its particular details' (Heraclitus of Ephesus, 535-475 bc).     

The adaptive significance of sexually dimorphic scale rugosity in sea snakes

In terrestrial snakes, rugose scales are uncommon and (if they occur) generally are found on both sexes. In contrast, rugose scales are seen in most sea snakes, especially in males. Why has marine life favored this sex-specific elaboration of scale rugosity? We pose and test alternative hypotheses about the function of rugose scales in males of the turtle-headed sea snake (Emydocephalus annulatus) and conclude that multiple selective forces have been involved. First, rugosities may aid male positioning during courtship, because histology shows that tubercles are more highly innervated than adjacent flat areas of each scale and hence are presumably more sensitive to tactile cues, and because biomechanical tests show that rugosities enhance friction between the bodies of males and females. Second, the occurrence of rugosities over the entire body of males and (albeit less well developed) in females as well suggests that rugosities also play a hydrodynamic role by modifying water flow across the snake's surface. Flow tank tests show that rugosities reduce the thickness of the boundary layer by almost 50% and create turbulent flow that should massively enhance rates of cutaneous oxygen uptake and hence prolong maximal courtship duration by males.