Molecular evolution of the Sex-Ratio inversion complex in Drosophila pseudoobscura: analysis of the Esterase-5 gene region

The Sex-Ratio chromosome in Drosophila pseudoobscura is subject to meiotic drive. It is associated with a series of three nonoverlapping paracentric inversions on the right arm of the X chromosome. The esterase-5 gene region has been localized to section 23 within the subbasal inversion of the Sex-Ratio inversion complex, making esterase- 5 a convenient locus for molecular evolutionary analyses of the Sex- Ratio inversion complex and the associated drive system. A 504-bp fragment of noncoding, intergenic DNA from the esterase-5 gene region was amplified and sequenced from 14 Sex-Ratio and 14 Standard X chromosomes of D. pseudoobscura, and from 9 X chromosomes of its two sibling species, Drosophila persimilis and Drosophila miranda. There is extensive sequence differentiation between the Sex-Ratio and Standard chromosomal types. The common Standard chromosome is highly polymorphic, while, as expected from either the neutral mutation theory or the selective sweep hypothesis, the rarer Sex-Ratio chromosome has much less within-chromosome nucleotide polymorphism. We estimate that the Standard and Sex-Ratio chromosomes in D. pseudoobscura diverged between 700,000 and 1.3 Mya, or at least 2 million generations ago. The clustering of D. pseudoobscura Sex-Ratio chromosomes in a neighbor- joining phylogeny indicates a fairly old, monophyletic origin in this species. It appears from these data that Sex-Ratio genes were present prior to the divergence of D. pseudoobscura and D. persimilis and that both the Standard and Sex-Ratio chromosomes of D. persimilis were derived from the Standard chromosome of D. pseudoobscura after the inversion events that isolated the D. pseudoobscura Sex-Ratio chromosome.      

IDENTIFICATION OF LECTINS IN THE KINETIDS OF TETRAHYMENA PYRIFORMIS

Previously we described lectin-like molecules in the ciliate Tetrahymena pyriformis; by application of synthetic neoglycoconjugates it is now shown that T. pyriformis contains considerable amounts of both a β-d-glucose- and a lactose-specific lectin. No evidence for the presence of α-d-mannose-, α-d-galactose- or of α-l-fucose-specific lectins could be obtained. The two lectins, identified in T. pyriformis, are associated with the kinetids. During cell division the lectins disappear or become masked in the fission furrow. Therefore, we assume that these lectins are involved in the organization of the distribution pattern of the kinetids during cell division perhaps due to lectin—glycoprotein interactions.     

Increased collagen metabolism in granulomata induced in rats deficient in endogenous prostaglandin precursors

Collagen metabolism was measured (in terms of various hydroxyproline (HP), DNA and protein ratios) in granulomata obtained after s.c. implantation of carrageenan-impregnated and untreated polyether sponges into normal and essential fatty acid deficient (EFAD) rats for 8 and 15 days. Collagen synthesis (HP/protein) in day 8 and 15 untreated granulomata was the same for both normal and EFAD rats, though collagen breakdown (total HP) appeared to be greater in EFAD granulomata on day 15. With carrageenan-impregnated sponges, collagen synthesis in EFAD granulomata was much greater than in normal granulomata on both day 8 and day 15. Ratios of protein and/or HP to DNA (probably indicative of cellular infiltration) were increased in EFAD rats with both sponge types, though this increase was less pronounced with carrageenan-impregnated sponges. Is is suggested that endogenous prostaglandin (PG) production (markedly reduced during EFA deficiency) may exert a negative feedback effect on collagen metabolism during proliferative inflammation.     

Tube-Like Structures with Co-Expression of D2-40 and CD34: Newly Formed Vasculatures?

Background: A great number of in vitro and in vivo studies have suggested that many pathways or factors can stimulate angiogenesis and lymphangiogenesis, which facilitate tumor progression and metastasis. However, the morphological and immunohistochemical profile of newly formed vasculatures has not been elucidated, making it difficult to differentiate them from the pre-existing ones, and to identify their unique molecular profiles for diagnosis and therapeutic interventions.Experimental findings: As cytokeratin (CK)-19 is a well-recognized stem cell marker and CK-19-positive cells are frequently detected in the peripheral blood of patients with metastatic cancer, our recent studies have assessed the involvement of CK-19 in the formation of new vasculatures in primary colorectal cancer (CRC) tissues. Our studies showed that a subset of lymph node-positive cases harbored some isolated normal epithelial structures with distinct CK-19 immunostaining within an otherwise CK-19-negative background. These structures are exclusively located within or adjacent to lymphoid follicles and are often surrounded by tube-like structures expressing lymphatic endothelial marker D2-40. Similar structures are more frequently seen at the junctions between pre-invasive and invasive CRC with the following features: (1). they consist of a single layer of endothelial cells that express both D2-40 and CD34, (2). their endothelial walls are often incomplete with disseminated cells protruding into the adjacent stroma, and (3). they are exclusively associated with disseminated CK-19-positive cellsHypothesis: Based on these findings, we propose that these tube-like structures represent newly formed vasculatures, which are derived by the convergence of aberrant lymphocyte infiltration and tumor stem cells. Because of their close physical proximity, tumor stem cells within the epithelial and stromal components contribute equally and coordinately to the morphogenesis of new vasculatures, which constitutes the basis for the unique morphologic and immunohistochemical features of newly formed vasculatures. Our hypothesis appears to be applicable to all epithelium-derived cancers.     

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JOCB BULLETIN

Welcome to the JOCB Bulletin     

NMR assignments of the N-terminal domain of Nephila clavipes spidroin 1

The building blocks of spider dragline silk are two fibrous proteins secreted from the major ampullate gland named spidroins 1 and 2 (MaSp1, MaSp2). These proteins consist of a large central domain composed of approximately 100 tandem copies of a 35–40 amino acid repeat sequence. Non-repetitive N and C-terminal domains, of which the C-terminal domain has been implicated to transition from soluble and insoluble states during spinning, flank the repetitive core. The N-terminal domain until recently has been largely unknown due to difficulties in cloning and expression. Here, we report nearly complete assignment for all ¹H, ¹³C, and ¹⁵N resonances in the 14 kDa N-terminal domain of major ampullate spidroin 1 (MaSp1-N) of the golden orb-web spider Nephila clavipes.     

Temporal variability in the spatial and environmental determinants of functional metacommunity organization – stream fish in a human‐modified landscape

1. Quantifying the relative importance of environmental filtering versus regional spatial structuring has become an intensively studied area in the context of metacommunity ecology. However, most studies have evaluated the role of environmental and spatial processes using taxonomic data sets of single snapshot surveys. 2. Here, we examined temporal changes in patterns and possible processes behind the functional metacommunity organization of stream fishes in a human‐modified landscape. Specifically, we (i) studied general changes in the functional composition of fish assemblages among 40 wadeable stream sites during a 3‐year study period in the catchment area of Lake Balaton, Hungary, (ii) quantified the relative importance of spatial and environmental factors as determinants of metacommunity structure and (iii) examined temporal variability in the relative role of spatial and environmental processes for this metacommunity. 3. Partial triadic analysis showed that assemblages could be effectively ordered along a functional gradient from invertebrate consuming species dominated by the opportunistic life‐history strategy, to assemblages with a diverse array of functional attributes. The analysis also revealed that functional fish assemblage structure was moderately stable among the sites between the sampling periods. 4. Despite moderate stability, variance partitioning using redundancy analyses (RDA) showed considerable temporal variability in the contribution of environmental and spatial factors to this pattern. The analyses also showed that environmental variables were, in general, more important than spatial ones in determining metacommunity structure. Of these, natural environmental variables (e.g. altitude, velocity) proved to be more influential than human‐related effects (e.g. pond area, % inhabited area above the site, nutrient enrichment), even in this landscape with relatively low variation in altitude and stream size. 5. Pond area was, however, the most important human stressor variable that was positively associated with the abundance of non‐native species with diverse functional attributes. The temporal variability in the relative importance of environmental and spatial factors was probably shaped by the release of non‐native fish from fish ponds to the stream system during flood events. 6. To conclude, both spatial processes and environmental control shape the functional metacommunity organization of stream fish assemblages in human‐modified landscapes, but their importance can vary in time. We argue, therefore, that metacommunity studies should better consider temporal variability in the ecological mechanisms (e.g. dispersal limitation, species sorting) that determine the dynamics of landscape‐level community organization.     

Life history predicts advancement of avian spring migration in response to climate change

An increasing number of studies demonstrate that plant and animal phenologies such as the timing of bird migration have been advancing over the globe, likely as a result of climate change. Even closely related species differ in their phenological responses, and the sources of this variation are poorly established. We used a large, standardized dataset of first arrival dates (FAD) of migratory birds to test the effects of phylogenetic relationships and various life-history and ecological traits on the degree to which different species adapt to climate change by earlier migration in spring. Using the phylogenetic comparative method, we found that the advancement of FAD was greater in species with more generalized diet, shorter migration distance, more broods per year, and less extensive prebreeding molt. In turn, we found little evidence that FAD trends were influenced by competition for mating (polygamy or extra-pair paternity) and breeding opportunities (cavity nests). Our findings were robust to several potentially confounding effects. These evolutionary correlations, coupled with the low levels of phylogenetic dependence we found, indicate that avian migration phenology adapts to climate change as a species-specific response. Our results suggest that the degree of this response is fundamentally shaped by constraints and selection pressures of the species' life history, and less so by the intensity of sexual selection.