The relationship between the fatty acid profiles of the yolk and the embryonic tissue lipids: A comparison between the lesser black backed gull (Larus fuscus) and the pheasant (Phasianus colchicus)

Although substantial information is available regarding the fatty acid composition of lipids of the yolk and of the developing tissues of the chicken embryo, there is little knowledge on this topic for other avian species. The aim of the present study was to compare the yolk and embryonic tissue fatty acid profiles for a species selecting its food in the wild (the lesser black backed gull) with one fed on a standard commercial diet (the commercially reared pheasant). The fatty acid compositions of the yolk lipids were determined, and major differences were observed between the two species. In particular, the phospholipid of the gull yolk was enriched in 20:4n-6 and 22:6n-3 (18.8 and 7.1%, respectively, by weight of total fatty acids) in comparison with the pheasant (4.0 and 4.1%, respectively). The fatty acid compositions of the embryonic tissues were determined using eggs incubated in the laboratory. For the liver and heart, the fatty acid composition of the lipids in the two species reflected the initial yolk composition, with the gull tissue lipids generally containing higher proportions of 20:4n-6 and 22:6n-3 than those of the pheasant. In contrast, the fatty acid profiles of the brain phospholipid were essentially identical in the two species, with 20:4n-6 and 22:6n-3 comprising approximately 9 and 17%, respectively, of total fatty acids in both cases.     

The effect of tunicamycin on secreted glycosidases of Aspergillus niger

The catalytic activity of the two stable aggregation states of arginine decarboxylase, a dimer and a decamer, has been examined under a variety of conditions. The specific activity of the dimer was determined at pH 5.2, the optimum pH, over a very broad range of protein concentrations. It was found to be independent of concentration only above 5 μg/ml, and decreased to 0 at 0.02 μg/ml, suggesting that a concentration-dependent reassociation was occurring in the assay. At 0.58 μg/ml, the restoration of activity was time dependent. We conclude that, at pH 5.2, the decamer is active and the dimer is essentially inactive. The activities of the dimer and the decamer were also compared at neutral pH, by using increasing concentrations of either Na⁺, arginine, or protein to induce reassociation. All of these experiments are consistent with the idea that both species are equally active at this pH. Furthermore, the dependence of activity on arginine concentration is not hyperbolic at pH 7.2. The arginine decarboxylase dimer was modified by allowing one sulfhydryl group per monomer to react with 5,5′-dithiobis(2-nitrobenzoic acid). The modified dimer reassociates less readily than the native form, requiring higher concentrations of any of the three associating agents tried. The modified decamer, at both pH 5.2 and 7.4, and the modified dimer, at pH 7.4, retain approximately 60% of the activity of the untreated enzyme.     

Development of cell surface saccharides on embryonic pancreatic cells

Using a battery of seven lectin-ferritin conjugates as probes for cell surface glycoconjugates, we have studied the pattern of plasmalemmal differentiation of cells in the embryonic rat pancreas from day 15 in utero to the early postpartum stage. Our results indicate that differentiation of plasmalemmal glycoconjugates on acinar, endocrine, and centroacinar cells is temporally correlated with development and is unique for each cell type, as indicated by lectin-ferritin binding. Specifically, (a) expression of adult cell surface saccharide phenotype can be detected on presumptive acinar cells as early as 15 d in utero, as indicated by soybean agglutinin binding, and precedes development of intracellular organelles characteristic of mature acinar cells; (b) maturation of the plasmalemma of acinar cells is reached after intracellular cytodifferentiation is completed, as indicated by appearance of Con A and fucoselectin binding sites only at day 19 of development; conversely, maturation of the endocrine cell plasmalemma is accompanied by "loss" (masking) of ricinus communis II agglutinin receptors; and (c) binding sites for fucose lectins and for soybean agglutinin are absent on endocrine and centroacinar cells at all stages examined. We conclude that acinar, centroacinar, and endocrine cells develop from a common progenitor cell(s) whose plasmalemmal carbohydrate composition resembles most closely that of the adult centroacinar cell. Finally, appearance of acinar lumina beginning at approximately 17 d in utero is accompanied by differenetiation of apical and basolateral plasmalemmal domains of epithelial cells, as indicated by enhanced binding of several lectin-ferritin conjugates to the apical plasmalemmal, a pattern that persists from this stage through adult life.     

Age-Specific Mortality During the 1918 Influenza Pandemic: Unravelling the Mystery of High Young Adult Mortality

The worldwide spread of a novel influenza A (H1N1) virus in 2009 showed that influenza remains a significant health threat, even for individuals in the prime of life. This paper focuses on the unusually high young adult mortality observed during the Spanish flu pandemic of 1918. Using historical records from Canada and the U.S., we report a peak of mortality at the exact age of 28 during the pandemic and argue that this increased mortality resulted from an early life exposure to influenza during the previous Russian flu pandemic of 1889–90. We posit that in specific instances, development of immunological memory to an influenza virus strain in early life may lead to a dysregulated immune response to antigenically novel strains encountered in later life, thereby increasing the risk of death. Exposure during critical periods of development could also create holes in the T cell repertoire and impair fetal maturation in general, thereby increasing mortality from infectious diseases later in life. Knowledge of the age-pattern of susceptibility to mortality from influenza could improve crisis management during future influenza pandemics.

“The war is over – and I must go” Egon Schiele, 1890–1918.

     

The cover of living and dead corals from airborne remote sensing

Trends in coral cover are widely used to indicate the health of coral reefs but are costly to obtain from field survey over large areas. In situ studies of reflected spectra at the coral surface show that living and recently dead colonies can be distinguished. Here, we investigate whether such spectral differences can be detected using an airborne remote sensing instrument. The Compact Airborne Spectrographic Imager (Itres Research Ltd, Canada) was flown in two configurations: 10 spectral bands with 1-m² pixels and 6 spectral bands with 0.25-m² pixels. First, we show that an instrument with 10 spectral bands possesses adequate spectral resolution to distinguish living Porites, living Pocillopora spp., partially dead Porites, recently dead Porites (total colony mortality within 6 months), old dead (>6 months) Porites, Halimeda spp., and coralline red algae when there is no water column to confuse spectra. All substrata were distinguished using fourth-order spectral derivatives around 538 nm and 562 nm. Then, at a shallow site (Tivaru) at Rangiroa Atoll, Tuamotu Archipelago (French Polynesia), we show that live and dead coral can be distinguished from the air to a depth of at least 4 m using first- and fourth-order spectral derivatives between 562–580 nm. However, partially dead and recently dead Porites colonies could not be distinguished from an airborne platform. Spectral differences among substrata are then exploited to predict the cover of reef substrata in ten 25-m² plots at nearby Motu Nuhi (max depth 8 m). The actual cover in these plots was determined in situ using quadrats with a 0.01-m² grid. Considerable disparity occurred between field and image-based measures of substrate cover within individual 25-m² quadrats. At this small scale, disparity, measured as the absolute difference in cover between field and remote-sensing methods, reached 25% in some substrata but was always less than 10% for living coral (99% of which consisted of Porites spp.). At the scale of the reef (all ten 25-m² quadrats), however, disparities in percent cover between imagery and field data were less than 10% for all substrata and extremely low for some classes (e.g. <3% for living Porites, recently dead Porites and Halimeda). The least accurately estimated substrata were sand and coralline red algae, which were overestimated by absolute values 7.9% and 6.6%, respectively. The precision of sampling was similar for field and remote-sensing methods: field methods required 19 plots to detect a 10% difference in coral cover among three reefs with a statistical power of 95%. Remote-sensing methods required 21 plots. However, it took 1 h to acquire imagery over 92,500 m² of reef, which represents 3,700 plots of 25 m² each, compared with 3 days to survey 10 such plots underwater. There were no significant differences in accuracy between 1-m² and 0.25-m² image resolutions, suggesting that the advantage of using smaller pixels is offset by reduced spectral information and an increase in noise (noise was observed to be 1.6–1.8 times greater in 0.25-m² pixels). We show that airborne remote sensing can be used to monitor coral and algal cover over large areas, providing that water is shallow and clear, and that brown fleshy macroalgae are scarce, that depth is known independently (e.g. from sonar survey).     

Evidence for placental transfer of lipids during gestation in the viviparous lizard, Pseudemoia entrecasteauxii

During gestation in the viviparous lizard Pseudemoia entrecasteauxii, the fetus obtains nutrients from two sources: uptake of yolk components from the retained egg (lecithotrophy) and transfer of nutrients from the maternal circulation via the placenta (placentotrophy). Although net placentotrophy in this species is indicated by the observation that the neonate contains 1.7 times more dry matter than the egg, the placental transfer of lipid has not been previously demonstrated. Lipid analysis was performed on newly ovulated eggs and on neonates. The weight of total lipid per neonate (8.2+/-0.5 mg) is significantly (P=0.049) greater than that in the egg (6.8+/-0.4 mg), indicating that the placenta must contribute some lipid to the fetus. On the assumption that 50% of the lipid delivered to the fetus from either source is oxidized for energy, it is calculated that the placenta accounts for 58.5% of the fetal lipid requirements, with the remaining 41.5% being derived from the egg. The fatty acid compositions of the triacylglycerol and phospholipid recovered in the neonatal tissue differ substantially from those of the egg. In particular, the proportions of 18:2n-6 and 18:3n-3 are far lower in the neonatal lipids compared with the egg lipids. On the other hand, the proportion of 22:6n-3 in the phospholipid of the neonate is six times higher than in the phospholipid of the egg. The absolute amount (mg) of 22:6n-3 recovered in the total lipid of the neonate is 3.8 times greater than the amount initially present in the egg. By comparison, the amount of total fatty acid in neonatal lipid is 1.2 times greater than the amount in the egg. Thus, there is a preferential use of 22:6n-3 for tissue phospholipid synthesis during development. We conclude that there is net transfer of fatty acids across the placenta to the fetus of P. entrecasteauxii and a high degree of selectivity in the use of the various fatty acids for fetal tissue lipid synthesis.     

2-(Anilinomethyl)imidazolines as alpha(1)-adrenoceptor agonists: the identification of alpha(1A) subtype selective 2'-carboxylic acid esters and amides

2-(Anilinomethyl)imidazolines with 2'-esters or 2'-amides are potent agonists of the cloned human alpha(1)-adrenoceptors in vitro. The size and shape of the ortho substituent can have significant effects on the potency, efficacy, and subtype selectivity of these 2-(anilinomethyl)imidazolines. alpha(1A)-subtype selective agonists have been identified.     

nifH sequences and nitrogen fixation in type I and type II methanotrophs

Some methane-oxidizing bacteria (methanotrophs) are known to be capable of expressing nitrogenase and utilizing N2 as a nitrogen source. However, no sequences are available for nif genes in these strains, and the known nitrogen-fixing methanotrophs are confined mainly to a few genera. The purpose of this work was to assess the nitrogen-fixing capabilities of a variety of methanotroph strains. nifH gene fragments from four type I methanotrophs and seven type II methanotrophs were PCR amplified and sequenced. Nitrogenase activity was confirmed in selected type I and type II strains by acetylene reduction. Activities ranged from 0.4 to 3.3 nmol/min/mg of protein. Sequence analysis shows that the nifH sequences from the type I and type II strains cluster with nifH sequences from other gamma proteobacteria and alpha proteobacteria, respectively. The translated nifH sequences from three Methylomonas strains show high identity (95 to 99%) to several published translated environmental nifH sequences PCR amplified from rice roots and a freshwater lake. The translated nifH sequences from the type II strains show high identity (94 to 99%) to published translated nifH sequences from a variety of environments, including rice roots, a freshwater lake, an oligotrophic ocean, and forest soil. These results provide evidence for nitrogen fixation in a broad range of methanotrophs and suggest that nitrogen-fixing methanotrophs may be widespread and important in the nitrogen cycling of many environments.     

alpha(1)-Adrenoceptor agonists: the identification of novel alpha(1A )subtype selective 2'-heteroaryl-2-(phenoxymethyl)imidazolines

Novel 2'-heteroaryl-2-(phenoxymethyl)imidazolines have been identified as potent agonists of the cloned human alpha(1)-adrenoceptors in vitro. The nature of the 2'-heteroaryl group can have significant effects on the potency, efficacy, and subtype selectivity in this series. alpha(1A) Subtype selective agonists have been identified.