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D M Carlson

Publications and source records attributed to D M Carlson.

At least 73 records · Page 4Linked to original sources
PubMed1982

Substructure of granules from serous cells of porcine tracheal submucosal glands.

The ultrastructure of serous cells from porcine tracheal submucosal glands was studied by conventional transmission electron microscopy (TEM), and by cytochemical methods to stain for complex carbohydrates. In tissue fixed and processed for TEM, and stained with uranyl acetate and lead citrate, the condensing granules of serous cells occasionally possessed a hexagonal and sometimes a lamellar substructure. Tissue fixed in paraformaldehyde-glutaraldehyde and stained with periodic acid-thiocarbohydrazide-silver proteinate (PTS) or with phosphotungstic acid (PTA) showed secretory granules stained for complex carbohydrates and revealed a substructure similar to that noted in the condensing granules. The dark staining substructure revealed by either the PTS or the PTA technique appeared to correspond to electron-lucent areas observed in the condensing granules by conventional TEM. The PTS staining probably demonstrated the presence of neutral glycoprotein, since the serous-cell granules did not react with a dialyzed iron stain for acidic glycoproteins. Treatment of periodic acid oxidized thin sections with pronase or pepsin prior to thiocarbohydrazide and silver proteinate treatment decreased the intensity of the PTS staining, but did not digest away any components of the granules. The substructure revealed by the carbohydrate stains may be a reflection of the mechanism of packaging or the macromolecular structure of the glycoproteins in the serous-cell granules.

Animals↗
PubMed1981

Galactosyltransferase activities in rat intestinal mucosa. Inhibition of nucleotide pyrophosphatase.

Nucleotide pyrophosphatase, a Zn2+-dependent enzyme catalyzing the hydrolysis of sugar nucleotides, generally interferes with glycosyltransferase assays. Certain tissues such as intestinal mucosa are particularly rich sources of nucleotide pyrophosphatase activity. The inhibition of nucleotide pyrophosphatase without affecting glycosyltransferase activities by the removal of Zn2+ allows for the assay of galactosyltransferases in rat intestinal particulate fractions. Inactivation of nucleotide pyrophosphatase was achieved by preincubation of particulate enzyme preparations in the presence of EDTA. Addition of Mn2+, required for the galactosyltransferase assays, did not reactivate the nucleotide pyrophosphatase. The presence of 0.05% (w/v) soybean trypsin inhibitor was required during the preparation of intestinal mucosa homogenates and enzyme assays to protect the UDP-galactose: N-acetylglucosaminyl galactosyltransferase from inactivation.

Animals↗
PubMed1981

Changes in galactosyltransferase activity in chick pectoral muscle during embryonic development.

The two major vertebrate galactosyltransferases have been investigated in developing chick muscle in ovo and in vitro, and in cultured chick fibroblasts. The two enzymes were UDP-galactose-N-acetylglucosamine galactosyltransferase (galactosyltransferase I) and UDP-galactose-N-acetylgalactosamine galactosyltransferase (galactosyltransferase II). Both activities fell during muscle development in ovo. Galactosyltransferase I activity was constant from day 7 to day 16, after which it declined 5-fold, whereas galactosyltransferase II activity fell markedly from day 9 to 13 and 16 to 20, displaying an overall 8-fold decrease. In primary muscle cultures, galactosyltransferase I activity fell slightly during 7 days in culture, whereas galactosyltransferase II increased 2-fold during the same period. No significant change in activity of either galactosyltransferase was observed during intercellular recognition and fusion. Analysis of muscle cultures treated with cytosine arabinoside and of fibroblast cultures revealed that the majority of galactosyltransferase I activity in primary muscle cultures is associated with fibroblasts, whereas the majority of galactosyltransferase II activity is muscle-associated. The addition of 5-bromodeoxyuridine to primary muscle cultures resulted in a 3-fold rise in activities of both transferases.

Animals↗
PubMed1979

Mechanism of phosphoacetylglucosamine mutase.

Kinetic studies of phosphoacetylglucosamine mutase (EC 2.7.5.2) for the following reactions: 1) Glc-1-P in equilibrium Glc-6-P and 2) GlcNAc-1-P in equilibrium GlcNAc-6-P have been conducted in the presence of Glc-1,6-P2 and GlcNAc-1,6-P2, respectively. In the first reaction, the initial velocity studies at various concentrations of one substrate showed a series of parallel lines in the Line-weaver-Burk plot when the concentrations of the other substrate were changed at several fixed levels. For both reactions, the initial velocity studies performed at fixed ratios of both substrates showed linear lines in the double reciprocal plot. The competitive substrate inhibition pattern was observed in the second reaction. A ping-pong mechanism is proposed for phosphoacetyl-glucosamine mutase. In addition, phosphoacetylglucosamine mutase can be phosphorylated by the addition of Glc-1-[32P]P probably via the reaction of Glc-1-[32P]P with the phosphoenzyme followed by the release of glucose-monophosphate leaving the 32P with the phosphoenzyme. The linkage between the phosphoryl residue and enzyme is stable in acid, but labile in alkali, suggesting phosphoserine (or phosphothreonine) as the phosphorylated amino acid. Biphasic heat denaturation curves suggest the existence of heat-stable and heat-labile forms of this enzyme.

Acetylglucosamine↗
PubMed1979

Purification of proline-rich proteins from parotid glands of isoproterenol-treated rats.

Prolonged isoproterenol treatment of rats is known to cause hypertrophy and hyperplasia of the parotid glands. Our results show that a dramatic increase in the synthesis or accumulation in the parotid glands of a series of proteins rich in proline also occurs with isoproterenol treatment. After 10 days of treatment (5 mg of isoproterenol/day) these proline-rich proteins (PRPs) comprise more than 50% of the total soluble proteins in parotid gland homogenates. The PRPs are rapidly labeled in vivo by a single intraperitoneal injection of [3H]proline with maximum incorporation occurring at about 3. More than 90% of the [3h]proline found in parotid gland homogenates is incorporated into PRPs with less than 1% of the radioactivity in alpha-amylase. Tritium incorporated into PRPs was isolated as [3H]proline after acid hydrolysis. One acidic and six basic 3H-labeled PRPs were isolated from the 100,000 x g supernatant fraction of parotid gland homogenates by Sephadex G-100 and ion exchange chromatography. The six basic proteins accounted for about 90% of the total PRPs isolated.

Animals↗
PubMed1978

Preparation of glycopeptides and oligosaccharides from thyroxine-binding globulin.

Over 99% of thyroxine (T4), the major form of thyroid hormone in plasma, is bound to the plasma glycoprotein thyroxine-binding globulin (TBG). The carbohydrate composition of TBG (14.6% by weight) consists of mannose, galactose, N-acetylglucosamine, and N-acetylneuraminic acid in the molar ratios of 11:9:16:10 per mol of glycoprotein. No fucose or N-acetylgalactosamine were detected. Amino acid analyses were performed. Glycopeptides, prepared by exhaustive pronase treatment of the glycoprotein, were separated by gel filtration and ion exchange chromatography. All glycopeptides contained the four sugars present in the native glycoprotein. One-fourth of the glycopeptide fraction was resolved into a discrete component, glycopeptide I. The remaining glycopeptides were a mixture termed glycopeptides II and III. Glycopeptides II and III were resolved into two discrete carbohydrate units, termed oligosaccharides A and B, by alkaline-borohydride treatment and DEAE-cellulose chromatography. We propose that TBG contains four oligosaccharide chains as calculated from the molecular weights of the glycopeptides and from compositional data assuming 1 asparagine residue/glycopeptide. The carbohydrate structures of the glycopeptides and relative affinities of TBG, glycopeptides and oligosaccharides for hepatocyte plasma membrane binding are presented in the accompanying paper (Zinn, A.B., Marshall, J.S., and Carlson, D.M. (1978) J. Biol. Chem. 253, 6768-6773.

Amino Acids↗