Synchronisation of cell division in the shoot apex of Silene in relation to flower initiation

In plants of Silene coeli-rosa, induced to flower by 7 LD, synchronisation of cell division in 20 per cent or more of the cells in the shoot apical dome was found on the 8th and 9th days after the beginning of induction, during the plastochron before sepal initiation. Synchronisation was inferred from the changes in the proportions of cells with the 2C and 4C amounts of DNA, and changes in mitotic index and labelling index. From the peaks of mitotic index a cell cycle of 10 h was measured for the synchronised cells, half that of cells in the apices of uninduced plants in short days. The faster cell cycle and synchronisation in the induced plants was associated with a shortening, of both G1 and G2, suggesting two control points, while S and M remained unchanged. These results are compared with those from other plants in which synchronisation occurs at the beginning rather than the end of evocation.Abbreviations LD long day(s) - SD short day(s) - S DNA synthesis phase of cell cycle - G1 pre-S interphase - G2 post-S interphase - M mitosis     

Surface movement in water of splendipherin, the aquatic male sex pheromone of the tree frog Litoria splendida

The aquatic sex pheromone splendipherin (GLVSSIGKALGGLLADVVKSKGQPA-OH) of the male green tree frog Litoria splendida moves across the surface of water to reach the female. Surface pressure and X-ray reflectometry measurements confirm that splendipherin is a surface-active molecule, and are consistent with it having an ordered structure, whereby the hydrophilic portion of the peptide interacts with the underlying water and the hydrophobic region is adjacent to the vapour phase. The movement of splendipherin over the surface of water is caused by a surface pressure gradient. In order to better define the structure of splendipherin at the water/air interface we used 2D NMR studies of the pheromone with the solvent system trifluoroethanol/water (1 : 1 v/v). In this solvent system, splendipherin adopts a bent alpha helix from residues V3 to K21. The bending of the helix occurs in the centre of the peptide in the vicinity of G11 and G12. The region of splendipherin from V3 to G11 has well-defined amphipathicity, whereas the amphipathicity from G12 to A25 is reduced by K19 and P24 intruding into the hydrophobic and hydrophilic regions respectively. A helical structure is consistent with X-ray reflectometry data.     

Discovery and characterization of NVP-QAV680, a potent and selective CRTh2 receptor antagonist suitable for clinical testing in allergic diseases

Optimization of a 7-azaindole-3-acetic acid CRTh2 receptor antagonist chemotype derived from high throughput screening furnished a highly selective compound NVP-QAV680 with low nM functional potency for inhibition of CRTh2 driven human eosinophil and Th2 lymphocyte activation in vitro. The molecule exhibited good oral bioavailability in the rat, combined with efficacy in rodent CRTh2-dependent mechanistic and allergic disease models and was suitable for clinical development.     

Inhibition of ras-induced oocyte maturation by peptides from ras-p21 and GTPase activating protein (GAP) identified as being effector domains from molecular dynamics calculations

In the accompanying article, using molecular dynamics calculations, we found that the 66–77 and 122–138 domains in ras-p21 and the 821–827, 832–845, 917–924, 943–953, and 1003–1020 domains in GAP have different conformations in complexes of GAP with wild-type and oncogenic ras-p21. We have now synthesized peptides corresponding to each of these domains and coinjected them into oocytes with oncogenic p21, which induces oocyte maturation, or injected them into oocytes incubated with insulin that induces maturation by activating wild-type cellular ras-p21. We find that all of these peptides inhibit both agents but do not inhibit progesterone-induced maturation that occurs by a ras-independent pathway. The p21 66–77 and 122–138 peptides cause greater inhibition of oncogenic p21. On the other hand, the GAP 832–845 and 1003–1021 peptides inhibit insulin-induced maturation to a significantly greater extent. Since we have found that activated wild-type and oncogenic p21 activate downstream targets like raf differently, these GAP peptides may be useful probes for identifying elements unique to the wild-type ras-p21 pathway.     

Efficacy of in-feed probiotics against Aeromonas bestiarum and Ichthyophthirius multifiliis skin infections in rainbow trout (Oncorhynchus mykiss, Walbaum)

Aims:  The aim of this study was to assess the efficacy of in-feed probiotics as a preventive measure against skin infections caused by Aeromonas bestiarum and Ichthyophthirius multifiliis (Ich) in rainbow trout.
Methods and Results:  Fin rot was induced in fish by intradermal injection with 0·1 ml volumes containing 10⁵ cells per ml A. bestiarum at the base of the dorsal fin. Ich infections resulted from immersion in Ich-contaminated water. Each probiotic was administered orally [10⁸ cells per g feed for GC2 ( Aeromonas sobria ) and 10¹⁰ cells per g feed for BA211 ( Brochothrix thermosphacta )] for 14 days. Results showed that, after challenge with A. bestiarum , probiotics GC2 and BA211 led to 76% and 88% survival, respectively, in contrast to 22% survival for controls. Fish fed with probiotic GC2 had 100% survival after challenge with Ich compared with 2% for probiotic BA211 and 0% for controls. Analysis of innate immune responses revealed that probiotic GC2 promoted higher phagocytic activity, whereas probiotic BA211 led to enhanced respiratory burst activity.
Conclusion:  Of the two probiotics examined, GC2 was more effective in protecting against both fin rot and Ich. Each probiotic appeared to stimulate different pathways within the innate immune system.
Significance and Impact of the Study:  This is the first demonstration that probiotics can protect fish against surface infections. Furthermore, this is the first time a probiotic has been shown to protect against a eucaryotic pathogen, namely I. multifiliis .     

Characterisation of Nitric Oxide Synthase in Three Cnidarian-Dinoflagellate Symbioses

Background

Nitric oxide synthase (NOS) is an enzyme catalysing the conversion of L-arginine to L-citrulline and nitric oxide (NO), the latter being an essential messenger molecule for a range of biological processes. Whilst its role in higher vertebrates is well understood little is known about the role of this enzyme in early metazoan groups. For instance, NOS-mediated signalling has been associated with Cnidaria-algal symbioses, however controversy remains about the contribution of enzyme activities by the individual partners of these mutualistic relationships.

Methodology/Principal Findings

Using a modified citrulline assay we successfully measured NOS activity in three cnidarian-algal symbioses: the sea anemone Aiptasia pallida, the hard coral Acropora millepora, and the soft coral Lobophytum pauciflorum, so demonstrating a wide distribution of this enzyme in the phylum Cnidaria. Further biochemical (citrulline assay) and histochemical (NADPH-diaphorase) investigations of NOS in the host tissue of L. pauciflorum revealed the cytosolic and calcium dependent nature of this enzyme and its in situ localisation within the coral''s gastrodermal tissue, the innermost layer of the body wall bearing the symbiotic algae. Interestingly, enzyme activity could not be detected in symbionts freshly isolated from the cnidarians, or in cultured algal symbionts.

Conclusions/Significance

These results suggest that NOS-mediated NO release may be host-derived, a finding that has the potential to further refine our understanding of signalling events in cnidarian-algal symbioses.     

Inhibition by isonicotinyl hydrazide of pigment formation in higher plants

The inhibition of greening of illuminated etiolated maize seedlings by isonicotinyl hydrazide can be alleviated by serine or pyruvate. The similar inhibition in barley can be reversed only by pyruvate. In both plants earlier intermediates in the glycollate pathway and other related compounds were ineffective in overcoming the inhibition of greening produced by isonicotinyl hydrazide. In maize seedlings radioactivity from l-serine-[3-¹⁴C] is poorly incorporated into β-carotene, a typical chloroplast terpenoid, unless glycine and formate or, more effectively, glycine together with isonicotinyl hydrazide are supplied. These supplementations may minimize interconversion of serine and glycine, and hence dilution of radioactivity at C-3 of l-serine by unlabelled C-1 units, before incorporation into terpenoids. The results support the view that in young greening tissue the C2-3 fragment of l-serine can give rise to acetyl-CoA, an obligatory precursor of chloroplast terpenoids.