1,721,082 research outputs found
Guinea pig kidney β-N-acetylgalactosaminyltransferase towards Tamm-Horsfall glycoprotein. Requirement of sialic acid in the acceptor for transferase activity
No full textA β-N-acetylgalactosaminyltransferase that preferentially transferred N-acetylgalactosamine to Sd(a-) Tamm-Horsfall glycoprotein was found in guinea-pig kidney microsomal preparations. This enzyme was kidney-specific and was able to transfer the sugar to other glycoproteins, such as fetuin and α1-acidic glycoprotein. The presence of sialic acid in the acceptors was essential for the transferase activity when either glycoproteins or their Pronase glycopeptides were used as acceptors. Two glycoproteins (Tamm-Horsfall glycopeptides I and II) with a different carbohydrate composition were separated by DEAE-Sephacel chromatography from Pronase-digested Tamm-Horsfall glycoprotein. The amount of N-acetylgalactosamine transferred to glycopeptides by the enzyme correlated with their degree of sialylation. Enzymic digestion of N-[14C]acetylgalactosamine-labelled Tamm-Horsfall glycopeptide II showed that the transferred sugar was susceptible to β-N-hexosaminidase. The amount of sugar cleaved by β-hexosaminidase was strongly increased when the labelled Tamm-Horsfall glycopeptide II was pretreated with mild acid hydrolysis, a procedure that removed the sialic acid residues. Alkaline borohydride treatment of the labelled Tamm-Horsfall glycopeptide II did not release radioactivity, thus indicating that enzymic glycosylation took place at the N-asparagine-linked oligosaccharide units of Tamm-Horsfall glycoprotein
Corso di ebraico biblico
No full textSI TRATTA DI UN CORSO DI EBRAICO BIBLICO, 45 LEZIONI PROGRESSIVE E I RELATIVI ESERCIZI DA SVOLGERE PER APPRENDERE LA LINGUA DELL''ANTICO TESTAMENTO
TM and IRS-1C-PAN data fusion using multiresolution decomposition methods based on the ‘a tròus’ algorithm
No full textImages fusion represents an important tool for remote sensing data elaborations. This technique is used for many purposes. Very often it is used to produce improved spatial resolution. The most common situation is represented by a pair of images: the first acquired by a multispectral sensor with a pixel size greater than the pixel size of the second image given by a panchromatic sensor. Starting from these images fusion produces a new multispectral image with a spatial resolution equal, or close to that of the panchromatic sensor. Very often fusion introduces important distortions on the pixel spectra. This fact could compromise the extraction of information from the image, especially when using an automatic algorithm based on spectral signature such as in the case of image classification. In this work we present the analysis of two fusion methods based on multiresolution decomposition obtained using the “a tròus” algorithm and applied to a pair of images acquired by TM and IRS-1C-PAN sensors. The methods studied are also compared with two classical fusion methods, the IHS and the SPC. Fused results are studied and compared using various tests including supervised classification. Most of the tests used have been extracted from literature regarding the assessment of spatial and spectral quality of fused images. This study show that the methods based on multiresolution decomposition outperform the classical fusion methods considered with respect to spectral content preservation. Moreover, it is shown that some of the quality tests are more significant than others. The discussion of this last aspect furnishes important indications for data quality assessment methods.Image fusion represents an important tool for remote sensing data elaborations. This technique is used for many purposes. Very often it is used to produce improved spatial resolution. The most common situation is represented by a pair of images: the first acquired by a multispectral sensor with a pixel size greater than the pixel size of the second image given by a panchromatic sensor (PAN). Starting from these images fusion produces a new multispectral image with a spatial resolution equal, or close, to that of the PAN. Very often fusion introduces important distortions on the pixel spectra. This fact could compromise the extraction of information from the image, especially when using an automatic algorithm based on spectral signature such as in the case of image classification. In this work we present the analysis of two fusion methods based on multiresolution decomposition obtained using the 'a trous' algorithm and applied to a pair of images acquired by Thematic Mapper (TM) and Indian Remote Sensing (IRS)-1C-PAN sensors. The methods studied are also compared with two classical fusion methods, the intensity, hue and saturation (IHS) and standardized principal components (SPC). Fused results are studied and compared using various tests including supervised classification. Most of the tests used have been extracted from literature regarding the assessment of spatial and spectral quality of fused images. This study shows that the methods based on multiresolution decomposition outperform the classical fusion methods considered with respect to spectral content preservation. Moreover, it is shown that some of the quality tests are more significant than others. The discussion of this last aspect furnishes important indications for data quality assessment methods
Enhanced CMP‐NeuAc:Galβ1, 4GlcNAc‐R α2, 6 sialyltransferase activity of human colon cancer xenografts in athymic nude mice and of xenograft‐derived cell lines
No full textThe activity of an α2,6 sialyltransferase acting on N‐acetyllac‐tosaminic sequences (α2,6 ST E.G. 2.4.99.1) has previously been found to be increased in 90% of human colon cancer specimens. In the present study, the α2,6 ST activity of 6 human colon cancer cell lines grown in culture was compared with that expressed by the corresponding nude mice xenografts and by the cell lines derived from the xenografts. We found that xenografts of COLO 205, HT‐29, SW 620, SW 948 and SW 948 FL (a non‐adherent sub‐line of SW 948) cells express an α2,6 ST activity much higher than that of the in vitro‐grown cells. SW 48 cells grown either in culture or as xenografts lack the enzyme activity. All the xenograft‐derived cell lines except HT‐29 retained the increased α2,6 ST activity at least for the first 6 passages. Those derived from SW 948 xenografts showed an enrichment of round, non‐adherent cells, strongly reactive with the NeuAcα2,6Gal/GalNAc‐specific lectin from Sambucus nigra (SNA), thus indicating that a selection of these cells has occurred. Copyright © 1992 Wiley‐Liss, Inc., A Wiley Compan
Construction and characterization of centromeric, episomal and GFP-containing vectors for Saccharomyces cerevisiae prototrophic strains
No full textThe expression of soluble and cell-bound α2,6 sialyltransferase in human colonic carcinoma CaCo-2 cells correlates with the degree of enterocytic differentiation
No full textα2,6 sialyltransferase towards the N-acetyllactosaminyl sequence (α2,6 ST, E.C. 2.4.99.1) is one of the major sialyltransferases in human colonic cells; it strongly increases in human colorectal tumors and is largely expressed in fetal and neonatal rat colon. In this study we demonstrate that human colon carcinoma CaCo-2 cells,which differentiate spontaneously into enterocytes when maintained confluent for several days, exhibit a very high expression of α2,6 ST both in the cell-bound and soluble form. When the CaCo-2 cells were cultured on porous membranes the soluble α2,6 ST was mainly detected in the medium collected from the chamber corresponding to the basolateral face of the monolayer. The soluble α2,6 ST could be concentrated and purified from the α2,3 sialyltransferase by affinity chromatography on Blue Sepharose. © 1992 Academic Press, Inc
Characterization and partial purification of β-N-acetylgalactosaminyltransferase from urine of Sd(a+) individuals
No full textUrine from Sd(a+) individuals was found to contain a β-N-acetylgalactosaminyltransferase that transfers N-acetylgalactosamine (GalNAc) from UDP-GalNAc to 3′-sialyllactose and glycoproteins carrying the terminal NeuAcα-3Galβ group. This enzyme has been purified 174-fold by affinity chromatography on Blue Sepharose and DEAE-Sephacel chromatography in a yield of 33%. Neither endogenous incorporation nor sugar nucleotide degrading enzymes were found in the purified preparation. The transferase had a pH optimum of pH 7.5 and a requirement for Mn2+ but not for detergents. The Km for UDP-GalNAc was 66 × 10-6 m, using fetuin as an acceptor. Like β-GalNAc-transferase from other sources the urinary enzyme had a strict requirement for sialylated acceptors. On the basis of enzymatic and chemical treatment of the product obtained by the transfer of [3H]GalNAc to 3′-sialyllactose, we propose that the enzyme attaches GalNAc in β-anomeric configuration to 0-4 of the galactose residue that is substituted at O-3 by sialic acid. A preparation of Tamm-Horsfall glycoprotein from a Sd(a-) donor lacking β-Gal-NAc was found to be the best acceptor among the glycoproteins tested. Studies on the transferase activity toward fetuin, human chorionic gonadotropin, and glycophorin A indicated that the enzyme preferentially adds the sugar to the sialylated terminal end of N-linked oligosaccharides. Unlike the β-GalNAc-transferase bound to human kidney microsomes (F. Piller et al. (1986) Carbohydr. Res. 149, 171-184) the urinary transferase is able to transfer β-GalNAc to the NeuAcα-3Galβ-3(NeuAcα-6)GalNAc chains bound to the native glycophorin. © 1988
Tissue distribution and age-dependent expression of β-4-N-acetylgalactosaminyltransferase in guinea-pig
No full textGuinea-pig kidney contains β-4-N-acetylgalactosaminyltransferase which may be involved in the biosynthesis of the Sd a determinant expressed on Tamm-Horsfall glycoprotein. In the present study we show that this enzyme is expressed far more in the medulla than in the cortex of the kidney and that, among the other organs tested, is expressed only in colon and caecum. This transferase is ontogenically regulated, in that its activity is low at birth and increases as a function of age. From several aspects, the tissue distribution and the ontogenic expression of β-4-N-acetylgalactosaminyl-transferase and Tamm-Horsfall glycoprotein are similar. © 1987 Plenum Publishing Corporation
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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