Plant natriuretic peptide active site determination and effects on cGMP and cell volume regulation

Natriuretic peptides (NP) were first identified in animals where they play a role in the regulation of salt and water balance. This regulation is partly mediated by intracellular changes in cyclic GMP (cGMP). NP immunoanalogues occur in many plants and have been isolated, with two NP encoding genes characterised in <i>Arabidopsis thalianai> L. (<i>AtPNP-Ai> and <i>AtPNP-Bi>). Part of AtPNP-A contains the region with homology to human atrial (A)NP. We report here on the effects of recombinant AtPNP-A and smaller synthetic peptides within the ANP-homologous region with a view to identifying the biologically active domain of the molecule. Furthermore, we investigated interactions between AtPNP-A and the hormone, abscisic acid (ABA). ABA does not significantly affect <i>Arabidopsis i>mesophyll protoplast volume regulation, whereas AtPNP-A and synthetic peptides promote water uptake into the protoplasts causing swelling. This effect is promoted by the membrane permeable cGMP analogue, 8-Br-cGMP, and inhibited by guanylate cyclase inhibitors indicating that increases in cGMP are an essential component of the plant natriuretic peptides (PNP) signalling cascade. ABA does not induce cGMP transients and does not affect AtPNP-A dependent cGMP increases, hence the two regulators differ in their second messenger signatures. Interestingly, AtPNP-A significantly delays and reduces the extent of ABA stimulated stomatal closure that is also based on cell volume regulation. We conclude that a complex interplay between observed PNP effects (stomatal opening and protoplast swelling) and ABA is likely to be cell type specific.<br /><br />

Comparison of the flexibility of eight-membered tetrasiloxane and stannasiloxane rings: a crystallographic and computational study

The syntheses and crystal structures of the eight-membered <i>cycloi>-stannasiloxanes <i>cycloi>-[<i>ti>-Bu(OH)Si(OSnt-Bub>2b>O)b>2b>Si(OH)<i>ti>-Bu] (<b>1b>) and <i>cycloi>-{<i>ti>-Bub>2b>Si[OSn(CHb>2b>SiMeb>3b>)b>2b>O]b>2b>Si<i>ti>-Bub>2b>} (<b>2b>) as well as the synthesis of the six-membered <i>cycloi>-stannasiloxane <i>cycloi>-{<i>ti>-Bub>2b>Si[OSn(CHb>2b>SiMeb>3b>)b>2b>]b>2b>O} (<b>3b>) are reported. Compound <b>1b> crystallizes as its <i>transi> isomer, but the <i>cisi> isomer dominates in solution. In agreement with the experimentally obtained results, ab initio and DFT calculations on the model compounds <i>cycloi>-(Hb>2b>SiO)b>4b> (<b>4b>), <i>cycloi>-[Hb>2b>Si(OSnHb>2b>)OSiHb>2b>] (<b>5b>), <i>cycloi>-O(Hb>2b>SiOSnHb>2b>)b>2b>O (<b>6b>), and <i>cycloi>-[Hb>2b>Si(OSiHb>2b>)OSnHb>2b>] (<b>7b>) indicate that the energetic preference to adopt puckered structures increases and the ring flexibility decreases with an increasing number of tin atoms in the ring. The rich diversity of puckered conformations is attributed to the steric demand of the different organic substituents. <br />

The first spacer-bridged tetraorganodistannoxanes with a mixed double ladder structure

The reaction of Meb>3b>SiCHb>2b>Clb>2b>Sn(CHb>2b>)b>3b>SnClb>2b>Ph (<b>6b>) with (<i>ti>Bub>2b>SnO)b>3b> gave a statistical mixture of the corresponding tetraorganodistannoxanes whereas the reaction of the spacer-bridged ditin tetrachlorides RClb>2b>Sn(CHb>2b>)b>4b>SnClb>2b>R (<b>3b>, R = Meb>3b>CCHb>2b>; <b>4b>, R = Meb>2b>CHCHb>2b>; <b>10b>, R = Meb>3b>SiCHb>2b>) with the polymeric spacer-bridged ditin oxides [R(O)Sn(CHb>2b>)b>4b>Sn(O)R]b><i>ni>b> (<b>7b>, R = Meb>2b>CHCHb>2b>; <b>8b>, R = Meb>3b>CCHb>2b>; <b>11b>, R = Meb>3b>SiCHb>2b>) provided the mixed double ladder compounds {[R(Cl)Sn(CHb>2b>)b>4b>Sn(Cl)R][R(Cl)Sn(CHb>2b>)b>4b>Sn(Cl)R']Ob>2b>}b>2b> (<b>9b>, R = Meb>3b>CCHb>2b>, R' = Meb>2b>CHCHb>2b>; <b>12b>, R = Meb>3b>CCHb>2b>, R' = Meb>3b>SiCHb>2b>) in almost quantitative yield. In solution, <b>9b> and <b>12b> are in equilibrium with their corresponding dimers, as was evidenced by ¹¹⁹Sn NMR spectroscopy, molecular mass determination, and electrospray mass spectrometry. The molecular structures of <b>9b> and <b>12b> were established by single crystal X-ray diffraction.<br />

Complexes of the tripodal nitrilotrimethylenetrisphosphonic (H6L) and P,P',P''-triphenylnitrilotrimethylenetrisphosphinic (H3L) acids with the copper(II) ion. Synthesis and charaterization of [Hpy][Cu(H3L)(H2O)] and [Cu(HL)(py)]2.2Me2CO

The complexes [Hpy][Cu(Hb>3b>L)(H<i>2i>O)] <b>1b> (L⁶ = nitrilotrimethylenetrisphosphonate) and [Cu(HL°)(py)]b>2b>&middot;2Meb>2b>CO <b>2b> [(L°)³ = <i>P,P,P"i> -triphenylnitrilotrismethylenetrisphosphinate)] have been isolated and characterized by X-ray crystallography, near IR-visible spectroscopy and magnetic measurements. The structure determination has shown the complexes to be constituted by monomeric and dimeric units respectively. In the monomer the metal atom is surrounded by the phosphonate ligand and a water molecule, with a geometry between a trigonal bipyramid and a square pyramid. The two copper atoms in the dimer are held together by an arm of the tripod ligand, with a pyridine molecule as additional ligand, and display octahedral geometry. The presence of monomeric and dimeric species in aqueous solutions of <b>1b> and <b>2b> has been shown by ESMS studies. The formation in water solution of the dimer [{Cu(Hb>3b>L)}b>2b>]^2-, as a minor species, has been supported by potentiometric measurements, whereas only the monomeric anion [CuL°] has been ascertained to be present. In general the ligand Hb>3b>L° forms less stable copper(II) complexes than Hb>6b>L.<br /><br /><br />

Chemical characterisation of the oligosaccharides in hooded seal (Cystophora cristata) and Australian fur seal (Arctocephalus pusillus doriferus) milk

Carbohydrates were extracted from hooded seal milk, <i>Crystophora cristatai> (family Phocidae). Free oligosaccharides were separated by gel filtration and then purified by ion exchange chromatography, gel filtration and preparative thin layer or paper chromatography and their structures determined by ¹H-NMR. The hooded seal milk was found to contain inositol and at least nine oligosaccharides, most of which had lacto-<i>Ni>-neotetraose or lacto-N-neohexaose as core units, similar to those in milk of other species of Carnivora such as bears (Ursidae). Their structures were as follows: Gal(&beta;1-4)Glc (lactose); Fuc(α1-2)Gal(&beta;1-4)Glc (2&prime;-fucosyllactose); Gal(&beta;1-4)GlcNAc(&beta;1-3)Gal(&beta;1-4)Glc (lacto-<i>Ni>-neotetraose); Fuc(α1-2)Gal(&beta;1-4)GlcNAc(&beta;1-3)Gal(&beta;1-4)Glc (lacto-<i>Ni>-fucopentaose IV); Gal(&beta;1-4)GlcNAc(&beta;1-3)[Gal(&beta;1-4)GlcNAc(&beta;1-6)]Gal(1-4)Glc (lacto-<i>Ni>-neohexaose); Fuc(α1-2)Gal(&beta;1-4)GlcNAc(&beta;1-3)[Gal(&beta;1-4)GlcNAc(&beta;1-6)]Gal(&beta;1-4)Glc (monofucosyl lacto-<i>Ni>-neohexaose a); Gal(&beta;1-4)GlcNAc(&beta;1-3)[Fuc(α1-2)Gal(&beta;1-4)GlcNAc(&beta;1-6)]Gal(&beta;1-4)Glc (monofucosyl lacto-<i>Ni>-neohexaose b); Fuc(α1-2)Gal(&beta;1-4)GlcNAc(&beta;1-3)[Fuc(α1-2)Gal(&beta;1-4)GlcNAc(&beta;1-6)]Gal(&beta;1-4)Glc (difucosyl lacto-<i>Ni>-neohexaose); Gal(&beta;1-4)GlcNAc(&beta;1-3)Gal(&beta;1-4)GlcNAc(&beta;1-3)Gal(&beta;1-4)Glc (<i>parai> lacto-<i>Ni>-neohexaose); Fuc(α1-2)Gal(&beta;1-4)GlcNAc(&beta;1-3)Gal(&beta;1-4)GlcNAc(&beta;1-3)Gal(&beta;1-4)Glc (monofucosyl para lacto-<i>Ni>-neohexaose). Milk of the Australian fur seal, <i>Arctophalus pusillus doriferus i>(family Otariidae) contained inositol but no lactose or free oligosaccharides. These results, therefore, support the hypothesis that the milk of otariids, unlike that of phocids, contains no free reducing saccharides.<br />

Barriers to cross-fertilization between populations of a widely dispersed Polychaete species are unlikely to have arisen through gametic compatibility arms-races

Although there are theoretical reasons to suspect that gametic incompatibility may develop readily among populations of broadcast spawning marine invertebrates, there have been very few studies documenting geographic patterns of interpopulation incompatibility for any species. To address this we determined how successfully individuals of the intertidal serpulid polychaete, <i>Galeolaria caespitosai>, can cross-fertilize within and among populations from across temperate Australia. Fertilization assays revealed asymmetrical differences between very distantly located populations from different coasts, with near-complete incompatibility between eggs from Sydney with sperm from Adelaide, but the reverse cross (Adelaide eggs, Sydney sperm) was reasonably compatible. Although that pattern was congruent with a clear difference in <i>Cytochrome Bi> sequences between worms on the south and east coasts of Australia, we also detected some indication of interpopulation incompatibility within the genetic grouping on east coast, between two populations separated by only 220 km. We then assessed whether commonly proposed gametic compatibility arms-races could account for these patterns. Our results suggest reduced gametic compatibility may reduce a female's maximum fertilization potential, resulting in a cost to this potential mechanism for reducing polyspermy. Consequently, the apparently rapid development of reproductive barriers here seems unlikely to have been driven by arms-races involving sexual conflict over fertilization rate.<br />

A sex difference in the cortisol response to tail docking and ACTH develops between 1 and 8 weeks of age in lambs

It is important to understand factors that may influence responses to stress, as these factors may also influence vulnerability to pathologies that can develop when stress responses are excessive or prolonged. It is clear that, in adults, the sex of an individual can influence the cortisol response to stress in a stressor specific manner. Nevertheless, the stage of development at which these sex differences emerge is unknown. We tested the hypothesis that there are sex differences in the cortisol response to tail docking and ACTH in lambs of 1 and 8 weeks of age. We also established cortisol responses in males when tail docking was imposed alone and in combination with castration at these ages. In experiment 1, 1 and 8 week old male and female lambs were subjected to sham handling, tail docking or, in males, a combination of tail docking and castration. In experiment 2, we administered ACTH (1.0 IU/kg) to male and female lambs at 1 and 8 weeks of age. There were significant cortisol responses to all treatments at both ages. Sex differences in the cortisol responses to tail docking and ACTH developed between 1 and 8 weeks of age, with females having greater responses than males. The data suggest that the mechanism for the sex difference in response to tail docking may involve the adrenal glands. At both ages, in males, the cortisol response to the combined treatment of tail docking and castration was significantly greater than that for tail docking alone. <br />

Does obesity affect the quality of life of adolescents?

Abstract located in Obesity Facts: the European journal of obesity : Vol. 2 : Suppl. 2 : Abstract number :T2:PO.09<br />

Conditioned taste aversion reduces fox depredation on model eggs on beaches

<b>Context:b>&nbsp; Conditioned taste aversion (CTA) is induced by an association of a food item with a negative experience, such as illness, which causes animals to avoid subsequent consumption of that particular food item. Inducing CTA may help reduce depredation rates of threatened fauna where predator population control is undesirable, impractical or unsuccessful.<br /><b><br />Aimsb>:&nbsp; We investigated whether CTA could be induced among foxes (<i>Vulpesi> <i>vulpesi>) to model eggs which mimicked those of the threatened hooded plover (<i>Thinornis rubricollisi>).<br /><b><br />Methods: &nbsp;b> Model eggs treated with a potential CTA-inducing chemical (sodium carbonate) and control eggs free of the agent were exposed to fox depredation for 28 days to simulate a hooded plover incubation period. To investigate whether CTA would persist in wild foxes, we implemented a part-time agent treatment (an initial 14 day exposure period of model eggs with the CTA agent followed by a second 14 day period when model eggs were free of the agent).<br /><b><br />Key results:b>&nbsp; Similar intervals to the first depredation event were found for all model eggs regardless of treatment. After the first depredation event by foxes, the rate and likelihood of fox depredation was significantly lower in treated eggs than in control eggs. The likelihood or rate of depredation across the three treatments did not differ between the first and second periods.<br /><b><br />Conclusions:b> Our results suggest that during an exposure period of at least 28 days, CTA can be induced in wild foxes to eggs on beaches. Our results also suggest that 14 days may be insufficient time for wild foxes to develop a lasting CTA to familiar food items such as eggs.<br /><b><br />Implications:b>&nbsp; Treatment of eggs with a CTA-inducing chemical may present&nbsp;a viable alternative to traditional predator control techniques for hooded plovers, as well as other ground-nesting birds, provided that an extended exposure to the CTAinducing agent occurs.

Wireless sensor networks for in-situ image validation for water and nutrient management

Water and Nitrogen (N) are critical inputs for crop production. Remote sensing data collected from multiple scales, including ground-based, aerial, and satellite, can be used for the formulation of an efficient and cost effective algorithm for the detection of N and water stress. Formulation and validation of such techniques require continuous acquisition of ground based spectral data over the canopy enabling field measurements to coincide exactly with aerial and satellite observations. In this context, a wireless sensor in situ network was developed and this paper describes the results of the first phase of the experiment along with the details of sensor development and instrumentation set up. The sensor network was established based on different spatial sampling strategies and each sensor collected spectral data in seven narrow wavebands (470, 550, 670, 700, 720, 750, 790 nm) critical for monitoring crop growth. Spectral measurements recorded at required intervals (up to 30 seconds) were relayed through a multi-hop wireless network to a base computer at the field site. These data were then accessed by the remote sensing centre computing system through broad band internet. Comparison of the data from the WSN and an industry standard ground based hyperspectral radiometer indicated that there were no significant differences in the spectral measurements for all the wavebands except for 790nm. Combining sensor and wireless technologies provides a robust means of aerial and satellite data calibration and an enhanced understanding of issues of variations in the scale for the effective water and nutrient management in wheat.<br />

Relationship between indices of adiposity obtained by peripheral quantitative computed tomography and dual-energy X-ray absorptiometry in pre-pubertal children

<i><b>Background/Aim:b> i>The study investigated the relationship between indices of adiposity measured by peripheral quantitative computed tomography (pQCT) and dual-energy X-ray absorptiometry (DXA) in pre-pubertal children.<br /><br /><i><b>Subjects and methods:b> i>DXA-derived per cent body fat (%BF) was measured in 284 boys and 288 girls, aged 7–10 years. Cross-sections of the forearm (<i>ni>=427) and lower leg (<i>ni>=560) were obtained by pQCT to measure total cross-sectional area of the limb (Total CSA), Muscle CSA, Fat CSA, %Fat CSA (Fat CSA/Total CSA&times;100) and muscle density.<br /><br /><i><b>Results:b>i><b> b>Peripheral QCT-derived %Fat CSA in the forearm and lower leg correlated strongly with DXA-derived %BF (<i>ri>=0.83–0.89, <i>pi><0.01) in both boys and girls. However, forearm and lower leg %Fat CSA were higher than whole body %BF by 5% and 10%, respectively. A better prediction of whole-body %BF was achieved by including %Fat CSA, muscle density and height into a hierarchical regression model. Using sex-specific regression equations, 87.7% of the boys and 83.7% of the girls had a predicted %BF within 3% units of the %BF obtained by DXA.<br /><i><br /><b>Conclusion:b>i> In pre-pubertal children, pQCT measures of adiposity are strongly associated with whole-body per cent body fat. This reproducible method could be an alternative technique to estimate body composition in this population.<br />

Differential response to resistance training in CHF according to ACE genotype

<b>Background : b>The Angiotensin Converting Enzyme (ACE) gene may influence the risk of heart disease and the response to various forms of exercise training may be at least partly dependent on the ACE genotype. We aimed to determine the effect of ACE genotype on the response to moderate intensity circuit resistance training in chronic heart failure (CHF) patients.<br /><b><br />Methods :b> The relationship between ACE genotype and the response to 11 weeks of resistance exercise training was determined in 37 CHF patients (New York Heart Association Functional Class = 2.3 ± 0.5; left ventricular ejection fraction 28 ± 7%; age 64 ± 12 years; 32:5 male:female) who were randomised to either resistance exercise (<i>ni> = 19) or inactive control group (<i>ni> = 18). Outcome measures included <b><i>VOi>b>2peakb>b> power output and muscle strength and endurance. ACE genotype was determined using standard methods.<br /><b><br />Results :b> At baseline, patients who were homozygous for the I allele had higher <b>VOb>b><b>2peakb>b> (<i>pi> = 0.02) and peak power (<i>pi> = 0.003) compared to patients who were homozygous for the D allele. Patients with the D allele, who were randomised to resistance training, compared to non-exercising controls, had greater peak power increases (ID <i>pi> < 0.001; DD <i>pi> < 0.001) when compared with patients homozygous for the I allele, who did not improve. No significant genotype-dependent changes were observed in <i><b>VOb>i>b><b>2peakb>b>, muscle strength, muscle endurance or lactate threshold.<br /><b><br />Conclusion :b> ACE genotype may have a role in exercise tolerance in CHF and could also influence the effectiveness of resistance training in this condition.<br />