Counting chromosomes: not as easy as 1, 2, 3

Mammalian cells must count their X chromosomes to determine whether to initiate X chromosome inactivation. A region that may be important for X chromosome counting has been identified, but the puzzle pieces still do not quite fit.     

Cell polarity and locomotion,as well as endocytosis,depend on NSF

NEM-sensitive factor (NSF) is an essential protein required during membrane transport. We replaced part of the endogenous D. discoideum NSF gene (nsfA) by a PCR-mutagenised library and isolated 11 mutants temperature-sensitive (ts) for growth. Two of these have been studied in detail. As expected, both are ts for FITC-dextran uptake by macropinocytosis, for internalising their surface membrane (monitored with FM1-43) and for phagocytosis. However, after 10-20 minutes at 28 degrees C, they round up and cease to chemotax, move or cap ConA receptors. They fully recover when returned to 22 degrees C. These cells carry out a normal 'cringe' reaction in response to cAMP, indicating that the actin cytoskeleton and this signal transduction pathway are still functional at 28 degrees C. The behaviour of these mutants shows that NSF-catalysed processes are required not only for the different endocytic cycles but also for the maintenance of cell polarity. As cell locomotion depends on a cell having a polarity, the mutants stop moving at high temperature. A tentative model is proposed to explain the surprising link between membrane recycling and cell polarity revealed here.     

The Dream as Text, The Dream as Narrative

The concepts of text and narrative are reviewed in terms of their appropriate application to the study of dreams. It is proposed that, once experienced, all dreams are texts, but that not all of these texts are narratives. Blending Jung's proposal for the form of the average dream with basic terms from narratology, dream data are employed in order to examine the narrativity of dreams, and by way of inquiring into cognitive aspects of narrative structure. Questions about the relation between language and narrative structure on the one hand, and between dreaming and language on the other are also briefly taken up.     

Isolation,spectroscopic characterization,X-ray,theoretical studies as well as in vitro cytotoxicity of Samarcandin

Samarcandin 1, a natural sesquiterpene-coumarin, was isolated as well as elucidated from F. assa-foetida which has significant effect in Iranian traditional medicine because of its medicinal attitudes. The crystal structure of samarcandin was determined by single-crystal X-ray structure analysis. It is orthorhombic, with unit cell parameters a = 10.8204 (5) Å, b = 12.9894 (7) Å, c = 15.2467 (9) Å, V = 2142.9 (2) Å³, space group P2₁2₁2₁ and four symmetry equivalent molecules in the unit cell. Samarcandin was isolated in order to study for its theoretical studies as well as its cellular toxicity as anti-cancer drug against two cancerous cells. In comparison with controls, our microscopic and MTT assay data showed that samarcandin suppresses cancer cell proliferation in a dose-dependent manner with IC₅₀ = 11 μM and 13 for AGS and WEHI-164 cell lines, respectively. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) of the structure was computed by three functional methods and 6-311++G⁷ standard basis set. The optimized molecular geometry and theoretical analysis agree closely to that obtained from the single crystal X-ray crystallography. To sum up, the good correlations between experimental and theoretical studies by UV, NMR, and IR spectra were found.     

Review article. Starch: as simple as A, B, C?

Starch is the main carbohydrate reserve in plants and an important part of our nutrition. Increasingly, it is being seen by industry as a useful raw material to include in foodstuffs and with which to produce other carbon-based polymers. Our understanding of starch biosynthesis and chemistry has advanced rapidly over the last few years, but our knowledge of how this translates into structure and thence into physicochemical properties and function is still lacking. Here, we have reviewed this information with an emphasis on genetics and physical properties, especially using data from the model crop, pea (Pisum sativum L.).     

Immunomodulatory mast cells: negative, as well as positive, regulators of immunity

Mast cells can promote inflammation and other tissue changes in IgE-associated allergic disorders, as well as in certain innate and adaptive immune responses that are thought to be independent of IgE. However, mast cells can also have anti-inflammatory and immunosuppressive functions. Here, we review the evidence that mast cells can have negative, as well as positive, immunomodulatory roles in vivo, and we propose that mast cells can both enhance and later suppress certain features of an immune response.     

Historical biogeography: Geography as evolution,evolution as geography

Abstract

Despite a number of advances in method in recent years, biogeography remains a field with a poorly developed philosophical core. As a result, its historical and ecological sides remain as isolated from one another as ever. In this essay I argue that a more unified approach to biogeographic studies will become possible only when workers realise that it is necessary to reject absolute space, “geography as handmaiden” approaches to distribution problems in favour of structuralist models compatible with both probabilistic spatial interaction and deterministic phylogenetic kinds of thinking. Pros and cons of regionalist, vicariance, and panbiogeographic approaches are weighed in this regard; it is shown that the primary objections of the latter schools to the approach of the former are vitiated when one dwells on second-order, rather than first-order, interpretations of regional faunal structure. This approach makes it possible to construct joint taxonomic/spatial models conducive to pattern analysis; the latter permits the genesis of hypotheses that can be tested through independently conceived theories of process (such as vicariance). An example of the kind of pattern study envisioned, involving generalised track depiction, is briefly described. A suggested cycle of research is thus laid out in which systematic revision becomes a function of a joint “natural” spatial and phylogenetic/historical approach to the subject.     

Arabidopsis Cortical Microtubules Are Initiated along,as Well as Branching from,Existing Microtubules

The principles by which cortical microtubules self-organize into a global template hold important implications for cell wall patterning. Microtubules move along bundles of microtubules, and neighboring bundles tend to form mobile domains that flow in a common direction. The bundles themselves move slowly and for longer than the individual microtubules, with domains describing slow rotary patterns. Despite this tendency for colinearity, microtubules have been seen to branch off extant microtubules at ∼45°. To examine this paradoxical behavior, we investigated whether some microtubules may be born on and grow along extant microtubule(s). The plus-end markers Arabidopsis thaliana end binding protein 1a, AtEB1a-GFP, and Arabidopsis SPIRAL1, SPR1-GFP, allowed microtubules of known polarity to be distinguished from underlying microtubules. This showed that the majority of microtubules do branch but in a direction heavily biased toward the plus end of the mother microtubule: few grow backward, consistent with the common polarity of domains. However, we also found that a significant proportion of emergent comets do follow the axes of extant microtubules, both at sites of apparent microtubule nucleation and at cross-over points. These phenomena help explain the persistence of bundles and counterbalance the tendency to branch.