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At least 469 records · Page 26Linked to original sources
PubMed1992

A reappraisal of the measurement of glomerular filtration rate in pre-term infants.

Thirty-seven single-injection polyfructosan-S (PF-S, Inutest) and 98 continuous-infusion PF-S/creatinine clearance studies were performed in 39 sick very low birth weight infants. The single-injection clearance method for measuring glomerular filtration rate has been shown to be a reliable technique if sampling is continued for 8 h or more and the PF-S (Inutest) assay is sensitive, accurate and precise. The continuous-infusion clearance method is also valid if the infusion is continued for more than 24 h and preceded by a loading dose in the form of a double-rate infusion for 8 h. Creatinine clearance is usually less than PF-S clearance, the mean ratio being 0.91, suggesting that there is some creatinine reabsorption in the renal tubule in sick very low birth weight infants.

Creatinine↗
PubMed1992

Resistance of in vivo-selected spontaneously transformed cells and Rous sarcoma virus-transformed cells to macrophage-mediated cytotoxicity.

The cytotoxic activity (CTA) of activated peritoneal macrophages (MP) on variant lines of Syrian hamster embryo (HE) cells of differing malignant characteristics was studied. The target cells were a line of low-malignant cells resulting from spontaneous transformation of HE cells in vitro (STHE strain), and malignant variants selected from them in vivo (STHE-LM-4, STHE-LM-8, and STHE-75/18 strains). In addition, we used cells of the HET-SR-1 strain; these are HE cells transformed in vitro by a tumorigenic Rous sarcoma virus (Schmidt-Ruppin strain, RSV-SR), or the TU-SR strain induced by RSV-SR in vivo. Thioglycollate-elicited peritoneal MP from Syrian hamsters were activated in vitro with bacterial levan, LPS or MDP and used as effector cells. MP-mediated cytolysis was determined by means of a 42-h radioactivity release assay with 3H-thymidine-labeled target cells. We found that only the parental STHE cells were susceptible towards fully-activated MP-mediated CTA. All three of the in vivo-selected malignant variants of the STHE cell sublines, as well as the tumorigenic RSV-SR transformants, were resistant to cytolysis by activated MP. Non-activated thioglycollate-elicited MP did not lyse any of the tumor cells studied.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1983

Spontaneous AKR lymphomas differ in their degree of malignancy and sensitivity to the polysaccharide levan.

Spontaneous AKR lymphomas differ in their biological behavior as judged by formation of local tumors at the site of inoculation, latency in the appearance of both local and distant tumors and mean survival time of the mice. Spontaneous AKR lymphomas differ markedly in their sensitivity to levan (polyfructose). An inverse correlation was observed between the degree of malignancy and sensitivity to levan.

Animals↗
PubMed2003

A novel and simple method for the purification of extracellular levansucrase from Zymomonas mobilis.

A new and simple method for the purification of extracellular levansucrase from Zymomonas mobilis from highly viscous fermentation broth was developed. After incubation of the fermentation broth with a fructose-polymer cleaving enzyme preparation (Fructozyme, Novozymes, DK) for 48 h, levansucrase precipitated as aggregates and was redissolved in a 3 M urea solution. By ongoing size-exclusion chromatography on Sephacryl S-300 the final levansucrase preparation was purified 100-fold and exhibited a specific activity of 25-35 U/mg(protein). The levansucrase was stable in 3 M urea solution for at least four months without inactivation. To maximize the enzyme yield the dynamic changes of extracellular levansucrase activity during fermentation were investigated. The highest levansucrase activity was observed during the logarithmic phase of growth (15-19 h of fermentation).

Centrifugation↗
PubMed2005

Production of levansucrase from Bacillus subtilis NRC 33a and enzymic synthesis of levan and Fructo-Oligosaccharides.

Bacillus subtilis NRC 33a was able to produce both inducible and constitutive extracellular levansucrase, respectively, using sucrose and glucose as carbon source. The optimal production of the levansucrase was at 30 degrees C. The effect of different nitrogen sources showed that baker's yeast with 2% concentration gave the highest levansucrase activity. Addition of 0.15 g/L MgSO(4) was the most favorable for levansucrase production. The enzymic synthesis of levan was studied using 60% acetone fraction. The results indicated that high enzyme concentrations produced increasing amounts of levan, and hence conversion of fructose to levan reached 84% using 1,000 microg/ml enzyme protein. Sucrose concentration was the most effective factor controlling the molecular weight of the synthesized levan. The conversion of fructose to levan was maximal at 30 degrees C. The time of reaction clearly affected the conversion of fructose to levan, which reached its maximum productivity at 18 hours (92%). Identification of levan indicated that fructose was the building unit of levan.

Bacillus subtilis↗
PubMed2000

Influence of yeast flocculation on the rate of Jerusalem artichoke extract fermentation.

Variations in residual sugar composition have been observed during Jerusalem artichoke extract fermentations by using Saccharomyces diastaticus NCYC 625, a flocculating yeast strain. In batch cultures, these differences were due to the inulin polymer size distribution of the extracts: measurements of enzymatic activities on different polymerized substrates have shown that the hydrolysis and fermentation yield decreased when the fructose/glucose ratio of the extract increased. Inulin hydrolysis appeared to be the limiting factor of the fermentation rate. A comparison of continuous and batch cultures with the same extract showed that fermentability differences were related to the structure and size of the yeast flocs. This led to an hydrolysis selectivity of the inulin polymers according to their size: the chemostat culture in which the floc average size was larger gave longer chained residual sugars.

Chromatography, High Pressure Liquid↗
PubMed2003

Expression of a yeast-derived invertase in companion cells results in long-distance transport of a trisaccharide in an apoplastic loader and influences sucrose transport.

Companion cell-specific expression of a cytosolic invertase from yeast ( Saccharomyces cerevisiae) was used as a tool to synthesise oligosaccharides in the sieve element/companion cell complex and study whether oligosaccharides could be transported in the phloem of an apoplastically loading species. Potato ( Solanum tuberosum L.) plants expressing the invertase under the control of the Agrobacterium tumefaciens rolC promoter produced the trisaccharide 6-kestose in leaves, which was transported via the phloem and accumulated in tubers of transgenic plants. In graft experiments with rolC invertase plants as scion and wild-type rootstocks, 6-kestose accumulated in tubers to levels comparable to sucrose. This shows that long-distance transport of oligosaccharides is possible in apoplastically loading plants, which normally transport only sucrose. The additional transport route for assimilates neither led to elevated photosynthetic activity nor to increased tuber yield. Enhanced sucrose turnover in companion cells caused large amounts of glucose and fructose to be exuded from leaf petioles, and elevated levels of sucrose were detected in phloem exudates. While the latter indicates a higher capacity for sucrose loading into the phloem due to increased metabolic activity of companion cells, the massive release of hexoses catalysed by the invertase seemed to interfere with assimilate delivery to sink organs.

Biological Transport↗
PubMed2006

Structural and functional features of fructansucrases present in Leuconostoc mesenteroides ATCC 8293.

Glycosyltransferases produced by Leuconostoc mesenteroides subsp. mesenteroides ATCC 8293 (equivalent to NRRL B-1118) were identified. Two glucansucrases and one fructansucrases were observed in batch culture while levC and levL genes, corresponding to two fructansucrases, were isolated from information obtained from the released draft sequence of this Leuconostoc strain genome and cloned in Escherichia coli. The recombinant enzymes were shown to be fructansucrases producing a polymer identified by NMR as levan, confirming our recent report stating that these are also mosaic levansucrases bearing structural features of glucansucrases in the amino and carboxy terminal regions, as is also the case of inulosucrase (IslA) from Leuconostoc citreum CW28 and levansucrase (LevS) from L. mesenteroides NRRL B-512F. The recombinant levansucrase LevC was purified and characterized in terms of pH, temperature, and kinetic properties. The enzyme exhibits Michaelis-Menten kinetic properties with a K(m) = 27.3 mM and a k(cat) = 282.9 s(-1). This levansucrase behaves mainly as a transferase as only 30% of the substrate is hydrolyzed in a wide range of sucrose concentrations, with higher hydrolytic activities at low substrate concentrations. With this report we experimentally confirm the unusual structural pattern displayed by fructansucrases present in Leuconostoc species that group as a novel sub family of fructansucrases.

Amino Acid Sequence↗
PubMed2005

Simultaneous and selective production of levan and poly(gamma-glutamic acid) by Bacillus subtilis.

Bacillus subtilis(natto) Takahashi, used to prepare the fermented soybean product natto, was grown in a basal medium containing 5% (w/w) sucrose and 1.5% (w/w) L-glutamate and produced 58% (w/w) poly(gamma-glutamic acid) and 42% (w/w) levan simultaneously. After 21 h, 40-50 mg levan ml-1 had been produced in medium containing 20% (w/w) sucrose but without L-glutamate. In medium containing L-glutamic acid but without sucrose, mainly poly(gamma-glutamic acid) was produced.

Bacillus subtilis↗
PubMed1979

The cell wall-associated levansucrase of Actinomyces viscosus.

Actinomyces viscosus produces both a soluble extracellular levansucrase and a cell wall-associated levansucrase. The enzyme from cell walls was solubilized by lysozyme digestion. The soluble extracellular and cell wall-associated forms of the enzyme were compared and appeared to be identical, based on molecular weight estimations, kinetic parameters, and reactions with antisera. The product of both forms of the enzyme was a high molecular weight, branched levan, as shown by its reactivity with myeloma proteins specific for beta(2 leads to 1) and for beta(2 leads to 6) linkages in fructosans. Although levansucrase remained tightly bound to the levan which it synthesized, the enzyme did not bind to exogeneously added levan. Regarding the potential pathogenicity of the levan product, pure levan, produced using purified levansucrase, did weakly activate complement by the alternative pathway. However, the pure levan did not directly cause bone resorption in an in vitro bone resorption assay.

Actinomyces↗
PubMed1990

The structural analysis of a levan produced by Streptococcus salivarius SS2.

The structure of a water-soluble levan produced by Streptococcus salivarius SS2 has been determined by means of various chemical and instrumental methods. Methylation and periodate oxidation studies demonstrate that the levan is comprised of D-fructofuranosyl backbone residues linked beta-(2----6) (about 70%) with beta-(2----1) branches (about 30%). 13C-N.m.r. spectral analysis of the polymer is consistent with the structure determined by chemical means.

Carbohydrate Sequence↗