Intracellular localization of GDP-l-fucose: Glycoprotein and CMP-sialic acid: Apolipoprotein glycosyltransferases in rat and pork livers

A GDP-l-fucose:glycoprotein fucosyltransferase which transfers l-fucose to terminal β-N-acetyl-d-glucosaminyl residues of sialidase-, β-galactosidase-treated α₁-acid glycoprotein and a CMP-sialic acid:glycoprotein sialyltransferase acting on sialidase-treated apolipoprotein-Ala₁ from human very low density lipoprotein have been shown to be concentrated in rat liver Golgi apparatus preparations at enrichments of 40- and 45-fold, respectively, and in pork liver Golgi-rich fractions at enrichments of 35- and 20-fold, respectively. A second fucosyltransferase acting on sialidase-treated α₁-acid glycopretein was absent from rat liver and was enriched only 13-fold in a pork liver Golgi-rich fraction. The smooth-surfaced microsome fraction was the only other rat liver subcellular fraction with appreciable levels of the GDP-l-fucose: β-N-acetyl-d-glucosaminide fucosyltransferase and the lipoprotein sialyltransferase (enrichments of 2.6- and 5.2-fold, respectivley). This enrichment could not be attributed to the plasma membrane content of the smooth microsome fraction since plasma membrane fractions from rat liver were shown to have relatively low concentrations of these two transferases (enrichments of 0.3 or less). Rat liver plasma membrane was also shown to have similarly low relative specific activities for three other glycosyltransferases (sialyl-, galactosyl-, and N-acetylglucosaminyl-). The accurate determination of the glycosyltransferase activities of the plasma membrane fraction required the use of relatively low concentrations of plasma membrane and relatively high concentrations of nucleotide-sugars in order to avoid interference by the high nucleotide-sugar pyrophosphatase and hydrolase activities of this fraction.     

Richness and abundance of stream fish communities in a fragmented neotropical landscape

Environmental Biology of Fishes - Environmental conditions influence ecological processes that shape stream community diversity and abundance. Deforestation has the potential to limit available...     

Revisiting the use of Iprodione and Trichoderma in the integrated management of onion white rot

The biocontrol properties of Trichoderma species are well documented, but their effectiveness in antagonism of the problematic Sclerotium cepivorum, the causal agent of white rot in Allium species, appears limited with reports of significant control only relating to deliberately-mutated strains of Trichoderma. Our previous studies have indicated the possibility of using selected naturally-occurring strains of the antagonist in the suppression of other diseases; now in vitro and controlled environment in vivo studies have indicated that a degree of control of Onion White Rot is possible, and that the selected antagonist strains can be used in integrated treatments with Iprodione to good effect. The possible value of such treatments is considered in light of other approaches to the suppression of this continuing problem.     

Differential recovery of membrane proteins after extraction by aqueous methanol and trifluoroethanol

Cell membrane proteome analysis is limited by inherent membrane hydrophobicity. Conventional membrane protein extraction techniques use detergents, chaotropes and organic acids that require sample clean-up or pH adjustment, and are associated with significant sample loss. We extracted membrane proteins from red blood cells (RBCs) using methanol (MeOH), trifluoroethanol (TFE) and urea, and identified membrane proteins using 2-D LC coupled with MALDI-TOF/TOF-MS. We show that organic solvents MeOH- and TFE-based methods have membrane protein analysis efficiencies comparable to urea, and are complementary for the recovery of both hydrophilic and hydrophobic peptides. The mean grand average of hydropathicity (GRAVY) value of identified peptides from the TFE-based method (-0.107) was significantly higher than that of the MeOH-based method (-0.465) (p<0.001). Sequential and adjunctive use of the organic solvents MeOH and TFE increases the number of proteins identified, and the confidence of their identification. We show that this strategy is effective for shotgun membrane proteome analysis.     

Pulmonary lymphatics and edema accumulation after brief lung injury

In a past study of hyperoxia-induced lung injury, the extensive lymphatic filling could have resulted from lymphatic proliferation or simple lymphatic recruitment. This study sought to determine whether brief lung injury could produce similar changes, to show which lymphatic compartments fill with edema, and to compare their three-dimensional structure. Tracheostomized rats were ventilated at high tidal volume (12-16 ml) or low tidal volume (3-5 ml) or allowed to breathe spontaneously for 25 min. Light microscopy showed more perivascular, interlobular septal, and alveolar edema in the animals ventilated at high tidal volume (P < 0.0001). Scanning electron microscopy of lymphatic casts showed extensive filling of the perivascular lymphatics in the group ventilated at high tidal volume (P < 0.01), but lymphatic filling was greater in the nonventilated group than in the group that was ventilated at low tidal volume (P < 0.01). The three-dimensional structures of the cast interlobular and perivascular lymphatics were similar. There was little filling and no difference in pleural lymphatic casts among the three groups. More edema accumulated in the surrounding lymphatics of larger blood vessels than smaller blood vessels. Brief high-tidal-volume lung injury caused pulmonary edema similar to that caused by chronic hyperoxic lung injury, except it was largely restricted to perivascular and septal lymphatics and prelymphatic spaces.     

Fungal cell wall phosphomannans facilitate the toxic activity of a plant PR-5 protein

Osmotin is a plant PR-5 protein. It has a broad spectrum of antifungal activity, yet also exhibits specificity for certain fungal targets. The structural bases for this specificity remain unknown. We show here that full sensitivity of Saccharomyces cerevisiae cells to the PR-5 protein osmotin is dependent on the function of MNN2, MNN4 and MNN6. MNN2 is an alpha-1, 2-mannosyltransferase catalyzing the addition of the first mannose to the branches on the poly l,6-mannose backbone of the outer chain of cell wall N-linked mannans. MNN4 and MNN6 are required for the transfer of mannosylphosphate to cell wall mannans. Null mnn2, mnn4 or mnn6 mutants lack phosphomannans and are defective in binding osmotin to the fungal cell wall. Both antimannoprotein antibody and the cationic dye alcian blue protect cells against osmotin cytotoxicity. MNN1 is an alpha-1,3-mannosyltransferase that adds the terminal mannose to the outer chain branches of N-linked mannan, masking mannosylphosphate. Null mnn1 cells exhibit enhanced osmotin binding and sensitivity. Several cell wall mannoproteins can bind to immobilized osmotin, suggesting that their polysaccharide constituent determines osmotin binding. Our results demonstrating a causal relationship between cell surface phosphomannan and the susceptibility of a yeast strain to osmotin suggest that cell surface polysaccharides of invading pathogens control target specificity of plant PR-5 proteins.