Detection and characterization of acidic compartments (vacuoles) in Chlorella vulgaris 11h cells by 31P-in vivo NMR spectroscopy and cytochemical techniques

Acidic inorganic phosphate (Pi) pool (pH around 6) was detected besides the cytoplasmic pool in intact cells of Chlorella vulgaris 11h by ³¹P-in vivo nuclear magnetic resonance (NMR) spectroscopy. It was characterized as acidic compartments (vacuoles) in combination with the cytochemical technique; staining the cells with neutral red and chloroquine which are known as basic reagents specifically accumulated in acidic compartments. Under various conditions, the results obtained with the cytochemical methods were well correlated with those obtained from in vivo NMR spectra; the vacuoles were well developed in the cells at the stationary growth phase where the acidic Pi signal was detected. In contrast, cells at the logarithmic phase in which no acidic Pi signal was detected contained only smaller vesicles that accumulated these basic reagents. No acidic compartment was detected by both cytochemical technique and ³¹P-NMR spectroscopy when the cells were treated with NH₄OH. The vacuolar pH was lowered by the anaerobic treatment of the cells in the presence of glucose, while it was not affected by the external pH during the preincubation ranging from 3 to 10. Possible vacuolar functions in unicellular algae especially with respect to intracellular pH regulation are discussed.Non-standard abbreviations EDTA ethylenediaminetetraacetic acid - HEPES N-2-hydroxyethylpiperazine-N-2-ethanesulfonic acid - MDP methylene diphosphonic acid - NMR nuelear magnetic resonance - PCA perchloric acid - PCV packed cell volume - Pi inorganic phosphate - Pic sytoplasmic inorganic phosphate - Piv vacuolar inorganic phosphate - ppm parts per million - SP sugar phosphates - TCA trichloroacetic acid     

Extracellular polysaccharides of cowpea rhizobia: compositional and functional studies

Polysaccharides excreted by cowpea Rhizobium strains JLn(c) and RA-1 were mixtures of complex acidic exopolysaccharides and low molecular weight neutral glucans. These polymers were fractionated using gel filtration chromatography. Purified fractions of the acidic heteropolymer reacted with peanut agglutinin to give precipitin bands when subjected to Ouchterlony gel diffusion. The acidic exopolysaccharide was found to contain mainly glucose, galactose, glucuronic acid, mannose and fucose. The non-carbohydrate substituents of the acidic heteropolymer were pyruvate, acetate and uronate which were identified by infrared and proton nuclear magnetic resonance spectroscopy as well as by chemical analysis.Abbreviations EPS Extracellular polysaccharide - YEM yeast extract mannitol - PNA peanut agglutination - ¹H-NMR proton nuclear magnetic resonance     

模拟酸雨对主要酸性土壤中铝的溶出及形态的影响

本文研究了模拟酸雨对主要酸性土壤中铝的溶出及形态变化的影响。结果表明,模拟酸雨对土壤酸化的影响较小,但对土壤铝的溶出却影响明显,尤其在pH<4.0时;模拟酸雨对不同类型土壤的影响是不同的,其中以高度风化的酸性土壤较为敏感。模拟酸雨对土壤游离铝形态的影响是重要的,酸处理后,交换性铝略有增加,无定形活性铝增加较多,而有机络合态铝有减少的趋势。这表明在酸雨的长期作用下,铝终将转化为交换性铝和水溶性铝而进入环境并危害生态系统。     

酸性水和投加铝、钙对鲢鱼早期发育和鳃超微结构的影响

在实验室条件下,研究了酸性水和投加铝、钙对鲢鱼胚胎孵化和鱼苗存活以及幼鱼鳃超微结构的影响。pH4.0引起所有胚胎在24小时内死亡,暴露于pH4.5—6.0的胚胎孵化率和暴露于pH4.0—6.0的5—15日龄鱼苗存活率随pH值上升而增高。投加0.5mg Al~(3+)/L使在酸性pH暴露条件下的胚胎孵化率和鱼苗存活率进一步降低。投加3.0mg Ca~(2+)/L可显著提高暴露于pH4.5和5.0的胚胎孵化率;投加2.0mg Ca~(2+)/L可在一定程度上提高暴露于pH4.5和5.0的鱼苗存活率。幼苗经pH4.5暴露8小时后出现严重的鳃超微结构损害;投加1.0mg Al~(3+)/L使鳃结构损害加剧;投加5.0mg Ca~(2+)/L可明显缓解酸性水对鳃的损害。     

Nitrification inhibition of added nitrogenous fertilisers by potassium chloride in soil

Summary Inhibitory effect of potassium chloride on nitrification of ammonium sulfate and urea in acid, neutral and calcareous soils was observed in an incubation study. In acidic soil, NO ₃ ^– –N production in soil treated with urea was retarded by addition of KCl. NO ₃ ^– –N concentration was much less even in comparison to control where ammonium sulfate and KCl were added together which might be due to cumulative effect of Cl^– and SO ₄ ^–2 ions. In neutral and calcareous soils, nitrification inhibition was less conspicuous.     

Bafilomycin A1 Inhibits the Action of Tetanus Toxin in Spinal Cord Neurons in Cell Culture

Abstract: Tetanus toxin (TeNT) is one of the clostridial neurotoxins that act intracellularly to block neurotransmitter release. However, neither the route of entry nor the mechanism by which these toxins gain access to the neuronal cytoplasm has been established definitively. In murine spinal cord cell cultures, release of the neurotransmitter glycine is particularly sensitive to blockade by TeNT. To test whether TeNT enters neurons through acidic endosomes or is routed through the Golgi apparatus, toxin action on potassium-evoked glycine release was assayed in cultures pretreated with bafilomycin A1 (baf A1) or brefeldin A (BFA). baf A1, which inhibits the vacuolar-type H⁺-ATPase responsible for endosome acidification, diminishes the staining of acidic compartments and interferes with the action of TeNT in a dose-dependent manner. TeNT blockade of evoked glycine release is inhibited by 50 and 90% in cultures pretreated with 50 and 100 n M baf A1, respectively, compared with cultures treated with the inhibitor alone. The effects of baf A1 are fully reversible. In contrast, BFA, which disrupts Golgi function, has no effect on TeNT action. These findings provide evidence that TeNT enters the neuronal cytoplasm through baf A1-sensitive acidic compartments and that TeNT is not trafficked through the Golgi apparatus before its translocation into the neuronal cytosol.     

Purification and partial characterization of an acidic ribosomal protein kinase from maize

Phosphorylation and dephosphorylation of ribosomal proteins have been suggested to participate in the regulation of protein synthesis in eukaryotic organisms. The present research focuses on the purification and partial characterization of a protein kinase from maize ribosomes that specifically phosphorylates acidic ribosomal proteins. Ribosomes purified from maize axes were used as the enzyme source. Purification of ribosomes was performed by centrifugation through a 0.5 M sucrose, 0.8 M KCl cushion. A protein kinase activity present in this fraction was released by extraction with 1.5 M KCl and further purified by diethylaminoethyl cellulose column chromatography. A peak containing protein kinase activity was eluted around 400 m M KCl. Analysis of this fraction by sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed one band of 38 kDa molecular mass, which cross-reacted in a western blot with antibodies raised against proteins from the large ribosomal subunit. This enzyme specifically phosphorylates one of the acidic ribosomal proteins (P₂). Its activity is inhibited by Ca²⁺ and Zn²⁺ and is activated by Mg²⁺, polylysine and spermine. The relevance of this protein kinase in reinitiating the protein synthesis process during germination is discussed.     

Structure of an acidic microcapsular glycan from the reference strain (C.D.C. 866-57) for Serratia marcescens serogroup 01

The structure of the acidic polysaccharide from Serratia marcescens serogroup O1 has been investigated. NMR spectroscopy together with sugar and methylation analysis have been used as well as a uronic acid degradation. The polysaccharide consists of pentasaccharide repeating units having the following structure.

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The polysaccharide also contains one equivalent of O-acetyl groups per repeating unit present on, inter alia, a hydroxymethyl group.     

Hydrolysis of cyclosporin A: Identification of 1,11 seco-cyclosporin A and 4,5 secoisoCyclosporin A by FAB-MS/MS

We have previously reported that treatment of CsA with aqueous HCl gives rise to the formation of a number of water-soluble compounds. Two of these were identified from their FAB-MS/MS spectra as open-chain nona- and decapeptides. We describe here the identification of two other main compounds deriving from the same treatment. Identification was rendered possible from the comparison of their FAB-MS/MS spectra with those of methyl and acetyl derivatives. The two compounds are water-soluble, open-chain undecapeptides corresponding to 1,11 seco-CsA and of 4,5 seco-isoCsA, respectively.     

Microbial production and uptake of nitric oxide in soil

Abstract Fluxes of NO from three different soils have been studied by a flow-through system in the laboratory as a function of gas flow rate, of NO mixing ratio, and of incubation conditions. The dependence of net NO fluxes on gas flow rates and on NO mixing ratios could be described by a simple model of simultaneous NO production and NO uptake. By using this model, rates of gross NO production, rate constants of NO uptake, and NO compensation mixing ratios could be determined as function of the soil type and the incubation condition. Gross NO production rates were one to two orders of magnitude larger under anaerobic than under aerobic conditions. NO uptake rate constants, on the other hand, were only 5–8 times larger so that the compensation mixing ratios of NO were in a range of about 1600–2200 ppbv under anaerobic and of about 50–600 ppbv under aerobic conditions. The different soils exhibited similar NO uptake rate constants, but the gross NO production rate and compensation mixing ratio was significantly higher in an acidic (pH 4.7) sandy clay loam than in other less acidic soils. Experiments with autoclaved soil samples showed that both NO production and NO uptake was mainly due to microbial metabolism.