Differential stimulation of rat lung particulate guanylate cyclase activity by atrial natriuretic peptide and sodium nitroprusside

The effects of alpha-rat atrial natriuretic peptide (alpha-rANP) and sodium nitroprusside on the activity of rat lung particulate guanylate cyclase were examined. The particulate guanylate cyclase in partially purified rat lung membranes was stimulated by both alpha-rANP and nitroprusside. The effects of alpha-rANP and nitroprusside were, however, not additive. Diamide and N-ethylmaleimide almost completely abolished the nitroprusside-mediated stimulation, while they had only moderate effects on the alpha-rANP-mediated stimulation of the enzyme activity. ATP potentiated the enzyme stimulation by alpha-rANP, whereas it had no effect on the nitroprusside-mediated stimulation. These findings suggest that the stimulation of lung particulate guanylate cyclase activity by alpha-rANP and nitroprusside is mediated by different mechanisms.     

First-principles study of Rashba effect in the (LaAlO3)2/(SrTiO3)2

We have performed first-principles density functional calculations for superlattice composed of two oxide insulators, (LaAlO₃)₂/(SrTiO₃)₂. Calculated band structures show interface-induced metallic states. We found electron doping in the TiO₂ layer at LaO interface and hole doping in the AlO₂ layer at SrO interface. Due to the built-in electric field at the interface, the interface states show spin splitting and vortex-like spin textures in momentum space, i.e. Rashba effect. Calculated Rashba coefficient α_R, 12.6 meV Å, is of the same order as that of the experimental value.     

Effects of intravenous injection of butyrate, valerate and their isomers on endocrine pancreatic responses in conscious sheep (Ovis aries)

1. The effects of intravenous injection of n-butyrate, iso-butyrate, n-valerate and iso-valerate on insulin and glucagon secretion was examined in conscious sheep. 2. Each sodium salt of the short chain fatty acids increased plasma insulin and glucagon concentrations in a dose-dependent manner (312-1250 mumol/kg body wt). 3. Both butyrate and valerate isomers with branched carbon chains had larger insulin releasing activity than isomers with straight carbon chains. 4. The glucagon responses to butyrate or valerate did not differ between the isomers with straight carbon chains and those with branched carbon chains. 5. Our results suggest that the receptive mechanism to short chain fatty acids, which may involve the nervous system, differs between the A cell and the B cell in sheep in vivo.     

Two new xanthone glycosides from Tripterospermum lanceolatum

Oleanolic acid, mangiferin, and two new xanthone glucosides, named lanceoside (1,8-dihydroxy-3,7- dimethoxyxanthone- 4-O-β-d-glucoside) and lancerin (C-4-β-d-glucosyl-1,3,7-trihydroxyxanthone), respectively, were isolated from the aerial parts of Tripterospermum lanceolatum.     

Algicidal activity of the thiazolidinedione derivative TD49 against the harmful dinoflagellate Heterocapsa circularisquama in a mesocosm enclosure

To assess the algicidal effects of the thiazolidinedione derivative TD49 on the unarmored dinoflagellate Heterocapsa circularisquama and to evaluate the response of the planktonic community and the environment to this chemical, we undertook mesocosm (1,300 L) and small-scale experiments. The reduction ratio for H. circularisquama in each experiment was dependent on the concentration of TD49. At a TD49 concentration >0.4 μM, the abundance of H. circularisquama decreased by 99 % in the small-scale experiment and by 84 % in the mesocosm during the initial 2 days. At 0.2 μM TD49, the abundance of H. circularisquama decreased by up to 85 % in the small-scale experiment, whereas the abundance in the mesocosm increased, implying the absence of an algicidal effect. The decrease in planktonic organisms, including H. circularisquama, following TD49 treatment was correlated with abrupt declines in culture pH and dissolved oxygen concentration. Following addition of TD49, there was a significant increase in the abundance of diatoms and cryptophyta species, and after 8 days, the dominant species in the TD49 treatments shifted to small pennate diatoms including Cylindrotheca and Entomoneis species. The growth of some species among the zooplankton community was promoted at low TD49 concentrations (≤0.4 μM), whereas high concentrations (≥1.0 μM) had a negative effect. This study demonstrates that TD49 is an effective agent for the control for H. circularisquama blooms and that large-scale mesocosms play a crucial role in assessing the application of algicides such as TD49 in natural environments.     

Why pollinators visit only a fraction of the open flowers on a plant: The plant's point of view

We analyze the so-called ‘exponential decay’ model of pollen transfer for the case in which pollinators visit a fraction of the open flowers on a plant. The analysis is limited to the simplest case of a self-incompatible species, in which self pollen does not interfere with seed set. Plants can manipulate the number of flowers visited per pollinator approach by adjusting attractiveness of flowers so as to maximize pollen export (male fitness). In the model the length of the visitation sequence that is optimal for the plant f? always decreases with pollen deposition rate k₁, pollen uptake rate k₂, and the number of pollinator approaches to the plant X, but increases with the total number of flowers F. We assume that the average number of pollinator approaches X increases with the total number of flowers F, but slower than proportionality. It then follows that the optimal fraction of flowers a pollinator visits after arriving on the plant (f?/F) decreases with the total number of flowers F. Furthermore, the male fitness gain per flower generally decreases with number of flowers, except for the condition of ‘inefficient’ pollen transfer with very small values of k₁, k₂, and X, or when the plant has only a few flowers. The latter conditions should favour high nectar production and mass blooming. The known range of parameters suggests that male fitness increases with the total number of flowers slower than proportionality.     

α-Amanitin-sensitive DNA-dependent RNA polymerase I from cherry salmon (Oncorhynchus masou) liver nuclei

DNA-dependent RNA polymerases I and II were purified approximately 3900- and 13300 fold, respectively, from a sonicated nuclear extract of the cherry salmon liver by column chromatographies on DEAE-Sephadex, heparin-Sepharose and DNA-cellulose. The RNA polymerases were examined with respect to template-specificity, the effects of Mn²⁺, Mg²⁺ and ammonium sulfate, α-amanitin sensitivity. Results showed that the RNA polymerase I differed from other eukaryotic RNA polymerase I in α-amanitin sensitivity.     

Role of vitronectin in embryonic rat endocardial cell migration in vitro

Summary Vitronectin is one of the extracellular matrices that mediate cell spreading and attachment in vitro. In the present paper, we demonstrate the involvement of vitronectin in the migration of cushion mesenchymal cells of the embryonic rat heart. Immunohistochemistry established the localization of vitronectin in the myocardial cells and in some of the cushion mesenchymal cells of the truncus arteriosus and atrioventricular canal. In vitro, vitronectin, fibronectin, and collagen type-I revcaled significant stimulating activity for cushion mesenchymal cell migration. The distance migrated by cushion mesenchymal cells cultured on vitronectin, collagen type-I, or both vitronectin and fibronectin was similar, but that on fibronectin was significantly shorter. Following the addition of anti-vitronectin IgG to the medium, the migration distance of cushion mesenchymal cells on fibronectin was remarkably increased. Most explants on vitronectin or on both vitronectin and fibronectin became detached from dishes after the addition of the antivitronectin antibody. Immunostaining revealed that cushion mesenchymal cells cultured on substrata other than vitronectin synthesized vitronectin. From these results, it is suggested that vitronectin is synthesized by myocardial cells and some cushion mesenchymal cells, and that vitronectin inhibits cell movement on fibronectin. This feature of vitronectin may be important in the regulation of the migration of cushion mesenchymal cell in vivo.     

Differential susceptibility of human trophoblastic (BeWo) and uterine cervical (HeLa) cells to Neospora caninum infection

Neospora caninum is an apicomplexan parasite, closely related to Toxoplasma gondii, and causes abortion and congenital neosporosis in cattle worldwide. Trophoblast cells act in mechanisms of innate immune defense at the fetal-maternal interface and no data are available about the interaction of Neospora with human trophoblasts. Thus, this study aimed to verify the susceptibility of human trophoblastic (BeWo) compared with uterine cervical (HeLa) cell lines to N. caninum. BeWo and HeLa cells were infected with different parasite:cell ratios of N. caninum tachyzoites and analyzed at different times after infection for cell viability using thiazolyl blue tetrazole and lactate dehydrogenase assays. Both cell lines were also evaluated for cytokine production and parasite infection/replication assays when pre-treated or not with Neospora lysate antigen (NLA) or human recombinant IFN-γ. Cell viability was increased up to 48 h of infection in both types of cells, suggesting that infection could inhibit early cell death and/or induce cell proliferation. Neospora infection induced up-regulation of the macrophage migration inhibitory factor (MIF), mainly in HeLa cells, which was enhanced by cell pre-treatment by NLA or IFN-γ. Conversely, parasite infection induced down-regulation of the transforming growth factor (TGF-β), mostly in BeWo cells, which was decreased with NLA or IFN-γ pre-treatment. HeLa cells were more susceptible to Neospora infection than BeWo cells and IFN-γ pre-treatment resulted in reduced infection indices in both cell lines. Control of parasite growth was mediated by IFN-γ through an indoleamine-2,3-dioxygenase-dependent mechanism in HeLa cells alone. Based on these results, we concluded that BeWo and HeLa cells are readily infected by N. caninum, although presenting differences in susceptibility to infection, cytokine production and cell viability. Thus, these host cells can be considered in comparative approaches to understand strategies used by N. caninum to survive at the maternal-fetal interface.     

Isolation of rat bone marrow mast lineage cells using Thy 1.1 and rat stem cell factor.

Recent reports have shown that various marrow-derived cell populations respond vigorously to recombinant rat stem cell factor (rrSCF164), one form of the kit-ligand. In the present study, we isolated cell populations from rat bone marrow using the Thy 1.1 antigen (an antigen that in the rat is differentially expressed on primitive hemopoietic progenitor cells) and fluorescently conjugated rrSCF164 (rrSCF164-PE). We show that rrSCF164 only stimulates cells that are enriched in the brightest Thy 1.1 populations (Thy 1.1bright). Numerous cell lines were generated by serial passage in rrSCF164 containing medium, and the prototypic cell lines have been designated SRT002 and SRT003. Each cell line retains the Thy 1.1bright phenotype and does not respond to interleukins (IL) 1-8, IL-10, granulocyte (G) colony-stimulating factor (CSF), granulocyte macrophage (GM) CSF, M-CSF, or crude preparations of mitogen-stimulated T-cell supernatants. The Thy 1.1bright population of rat marrow was subdivided into a subset that binds rrSCF164-PE (Thy 1.1bright, rrSCF164+). The majority of these cells possess certain characteristics in common with marrow-derived mast cells and the Thy 1.1bright, rrSCF164 responsive cell lines, having similar granule morphology, being metachromatic, and reacting positively with alcian blue. Moreover, rats treated with rrSCF164 displayed significant increases in Thy 1.1bright, rrSCF164+ cells in the bone marrow. These studies show that the combination of Thy 1.1 and rrSCF164 makes possible the isolation of a unique subset of rat bone marrow cells that differentially express the Thy 1.1 antigen and the cell surface receptor c-kit, the majority of which are morphologically similar to marrow-derived mast cells.