COMPARATIVE MORPHOLOGY AND TAXONOMIC STATUS OF GRACILARIOPSIS (GRACILARIALES,RHODOPHYTA)1

The vegetative organization and reproductive development of Gracilariopsis lemaneiformis (Bory) Dawson, Acleto et Foldvik [including Gracilaria sjoestedtii Kylin] were investigated. Our observations on spermatangial development and post-fertilization features establish that Gracilariopsis Dawson is distinct at the generic level from Gracilaria Greville, and ice propose the resurrection of Gracilariopsis Dawson as a result. Spermatangial parent cells of Gracilariopsis are superficial, initiated in pairs or groups of three by concavo-convex longitudinal and transverse divisions. Each spermatangial parent cell cuts off a single, colorless spermatangium distally by a transverse division. The female reproductive apparatus consists of a supporting cell that bears a two-celled carpogonial branch flanked by two sterile branches, as in Gracilaria. Likewise, up to six sterile cells fuse with the carpogonium after fertilization to produce a primary fusion cell that generates the gonimoblasts; however, a secondary fusion cell is absent. Inner gonimoblast cells unite with cytologically modified cells of the inner pericarp by means of secondary pit-connections. Tubular nutritive cells are absent. The gonimoblast consists of a central sterile tissue interconnected throughout by secondary pit-connections surmounted by a fertile layer composed of carposporangia aligned in straight chains. The distribution of Gracilariopsis is extended to Western Europe.     

Therapeutic implications of cancer stem cells

Most cancers comprise a heterogenous population of cells with marked differences in their proliferative potential as well as the ability to reconstitute the tumor upon transplantation. Cancer stem cells are a minor population of tumor cells that possess the stem cell property of self-renewal. In addition, dysregulation of stem cell self-renewal is a likely requirement for the development of cancer. This new model for cancer will have significant ramifications for the way we study and treat cancer. In addition, through targeting the cancer stem cell and its dysregulated self-renewal, our therapies for treating cancer are likely to improve.     

Formation of 4,4'-dimethoxytrityl-C-phosphonate oligonucleotides

Incomplete sulfurization during solid-phase synthesis of phosphorothioate oligonucleotides using phosphoramidite chemistry was identified as the cause of formation of two new classes of process-related oligonucleotide impurities containing a DMTr-C-phosphonate (DMTr=4,4'-dimethoxytrityl) moiety. Phosphite triester intermediates that failed to oxidize (sulfurize) to the corresponding phosphorothioate triester react during the subsequent acid-induced (dichloroacetic acid) detritylation with the DMTr cation or its equivalent in an Arbuzov-type reaction. This leads to formation of DMTr-C-phosphonate mono- and diesters resulting in oligonucleotides modified with a DMTr-C-phosphonate moiety located internally or at the 5'terminal hydroxy group. DMTr-C-phosphonate derivatives are not detected when optimized sulfurization conditions are employed.     

Quantifying structure-function uncertainty: a graph theoretical exploration into the origins and limitations of protein annotation

Since the advent of investigations into structural genomics, research has focused on correctly identifying domain boundaries, as well as domain similarities and differences in the context of their evolutionary relationships. As the science of structural genomics ramps up adding more and more information into the databanks, questions about the accuracy and completeness of our classification and annotation systems appear on the forefront of this research. A central question of paramount importance is how structural similarity relates to functional similarity. Here, we begin to rigorously and quantitatively answer these questions by first exploring the consensus between the most common protein domain structure annotation databases CATH, SCOP and FSSP. Each of these databases explores the evolutionary relationships between protein domains using a combination of automatic and manual, structural and functional, continuous and discrete similarity measures. In order to examine the issue of consensus thoroughly, we build a generalized graph out of each of these databases and hierarchically cluster these graphs at interval thresholds. We then employ a distance measure to find regions of greatest overlap. Using this procedure we were able not only to enumerate the level of consensus between the different annotation systems, but also to define the graph-theoretical origins behind the annotation schema of class, family and superfamily by observing that the same thresholds that define the best consensus regions between FSSP, SCOP and CATH correspond to distinct, non-random phase-transitions in the structure comparison graph itself. To investigate the correspondence in divergence between structure and function further, we introduce a measure of functional entropy that calculates divergence in function space. First, we use this measure to calculate the general correlation between structural homology and functional proximity. We extend this analysis further by quantitatively calculating the average amount of functional information gained from our understanding of structural distance and the corollary inherent uncertainty that represents the theoretical limit of our ability to infer function from structural similarity. Finally we show how our measure of functional "entropy" translates into a more intuitive concept of functional annotation into similarity EC classes.     

Scale-dependent feedback and regular spatial patterns in young mussel beds

In the past decade, theoretical ecologists have emphasized that local interactions between predators and prey may invoke emergent spatial patterning at larger spatial scales. However, empirical evidence for the occurrence of emergent spatial patterning is scarce, which questions the relevance of the proposed mechanisms to ecological theory. We report on regular spatial patterns in young mussel beds on soft sediments in the Wadden Sea. We propose that scale-dependent feedback, resulting from short-range facilitation by mutual protection from waves and currents and long-range competition for algae, induces spatial self-organization, thereby providing a possible explanation for the observed patterning. The emergent self-organization affects the functioning of mussel bed ecosystems by enhancing productivity and resilience against disturbance. Moreover, self-organization allows mussels to persist at algal concentrations that would not permit survival of mussels in a homogeneous bed. Our results emphasize the importance of self-organization in affecting the emergent properties of natural systems at larger spatial scales.     

Putative autocleavage of reovirus mu1 protein in concert with outer-capsid disassembly and activation for membrane permeabilization

Capsid proteins of several different families of non-enveloped animal viruses with single-stranded RNA genomes undergo autocatalytic cleavage (autocleavage) as a maturation step in assembly. Similarly, the 76 kDa major outer-capsid protein mu1 of mammalian orthoreoviruses (reoviruses), which are non-enveloped and have double-stranded RNA genomes, undergoes putative autocleavage between residues 42 and 43, yielding N-terminal N-myristoylated fragment mu1N and C-terminal fragment mu1C. Cleavage at this site allows release of mu1N, which is thought to be critical for penetration of the host-cell membrane during cell entry. Most previous studies have suggested that cleavage at the mu1N/mu1C junction precedes addition to the outer capsid during virion assembly, such that only a small number of the mu1 subunits in mature virions remain uncleaved at that site (approximately 5%). In this study, we varied the conditions for disruption of virions before running the proteins on denaturing gels and in several circumstances recovered much higher levels of uncleaved mu1 (up to approximately 60%). Elements of the disruption conditions that allowed greater recovery of uncleaved protein were increased pH, absence of reducing agent, and decreased temperature. These same elements allowed comparably higher levels of the mu1delta protein, in which cleavage at the mu1N/delta junction has not occurred, to be recovered from particle uncoating intermediates in which mu1 had been previously cleaved by chymotrypsin in a distinct protease-sensitive region near residue 580. The capacity to recover higher levels of mu1delta following disruption of these particles for electrophoresis was lost, however, in concert with a series of structural changes that activate the particles for membrane permeabilization, suggesting that the putative autocleavage is itself one of these changes.     

ZnT-8, A Pancreatic Beta-Cell-Specific Zinc Transporter

The zinc content in the pancreatic beta cell is among the highest of the body. Zinc appears to be an important metal for insulin-secreting cells as insulin is stored inside secretory vesicles as a solid hexamer bound with two Zn²⁺ ions per hexamer. Zinc is also an important component of insulin secretion mechanisms and is likely to modulate the function of neighbouring cells via paracrine/autocrine interactions. Therefore beta cells undoubtedly need very efficient and specialized transporters to accumulate sufficient amounts of zinc in secretion vesicles. We report here the discovery and the characteristics of a new zinc transporter, ZnT-8, belonging to the CDF (Cation Diffusion Facilitator) family and expressed only in pancreatic beta cells. This transporter, localized in secretion vesicles membrane, facilitates the accumulation of zinc from the cytoplasm into intracellular insulin-containing vesicles and is a major component for providing zinc to insulin maturation and/or storage processes in insulin-secreting pancreatic beta cells. We discovered mammalian orthologs (rat, mouse, chimpanzee, and dog) and found these ZnT-8 proteins very similar (98% conserved amino acids) to human ZnT-8, indicating a high conservation during evolution.     

The endothelial glycocalyx: a potential barrier between health and vascular disease

PURPOSE OF REVIEW: Although cardiovascular prevention has improved substantially, we still face the challenge of finding new targets to reduce the sequelae of atherosclerosis further. In this regard, optimizing the vasculoprotective effects of the vessel wall itself warrants intensive research. In particular, the endothelial glycocalyx, consisting of proteoglycans, glycoproteins and adsorbed plasma proteins, may play an essential role in protecting the vessel wall from atherosclerosis. RECENT DEVELOPMENTS: In this review, we will discuss the different vasculoprotective effects exerted by the endothelial glycocalyx, the factors that damage it, and the first preliminary data on the glycocalyx dimension in humans. Whereas most glycocalyx research has traditionally focused on the microvasculature, more recent data have underscored the importance of the glycocalyx in protecting the macrovasculature against pro-atherogenic insults. It has been shown that glycocalyx loss is accompanied by a wide array of unfavourable changes in both small and larger vessels. Pro-atherogenic stimuli increase the shedding of glycocalyx constituents into the circulation, contributing to the progressive loss of the vasculoprotective properties of the vessel wall. Novel techniques have facilitated reproducible measurements of systemic glycocalyx volume in humans. Consistent with experimental data, the volume of the human glycocalyx is also severely perturbed by exposure to atherogenic risk factors. SUMMARY: Cumulating evidence suggests that an intact glycocalyx protects the vessel wall, whereas disruption of the glycocalyx upon atherogenic stimuli increases vascular vulnerability for atherogenesis.