Satoru Tamura

Siena Heights University, Newark, New Jersey, United States

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Publications (8)24.58 Total impact

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    ABSTRACT: The intracellular transport of mucus glycoprotein precursor (apomucin) from endoplasmic reticulum (ER) to Golgi was quantitated by the immunoprecipitation with 3G12 antimucin monoclonal antibody and by estimation of the apomucin glycosylation using UDP-[3H]galactose. The assembly of the entities carrying apomucin to Golgi was assessed by electron microscopy and by quantitation of the incorporation of [14C]choline, [14C]ethanolamine, and [14C]oleic acid into their lipids. The microscopic image of the isolated transport components revealed a population of 80- to 100-nm vesicles with occasional membranes of the ER used for their synthesis. On the average, the vesicles contained 82 ng apomucin/microgram of protein and 80-90% of the total incorporated lipid precursors. From that, 91% of [14C]choline was detected in phosphatidylcholine, and 9% in phosphatidylethanolamine, lysophosphatidylcholine, and sphingomyelin. With [14C]oleate, 54% of the label was incorporated into ceramide, diglyceride, and phosphatidic acid, 35% to phosphatidylcholine, 7% in phosphatidylethanolamine, and 2% in sphingomyelin. After incubation of the vesicles with Golgi, the apomucin was found glycosylated and the lipids of the transport vesicles incorporated into Golgi membranes. The fusion of the vesicular membranes was accompanied by the synthesis of sphingomyelin. In the Golgi, 39-55% of the radiolabeled phosphatidylcholine of transport vesicles was converted to sphingomyelin. The results indicate that the newly synthesized membranes of apomucin transporting vesicles are enriched in phosphoglycerides and ceramides. Upon fusion with the Golgi, the membranes of the vesicles are replenished with sphingomyelin by exchange reaction between phosphatidylcholine and ceramide.
    Archives of Biochemistry and Biophysics 11/1992; 298(1):167-75. · 3.04 Impact Factor
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    ABSTRACT: The intracellular transport of mucus glycoprotein precursor (apomucin) from endoplasmic reticulum (ER) to Golgi was quantitated by the immunoprecipitation with 3G12 antimucin monoclonal antibody and by estimation of the apomucin glycosylation using UDP-[3H]galactose. The assembly of the entities carrying apomucin to Golgi was assessed by electron microscopy and by quantitation of the incorporation of [14C]choline, [14C]ethanolamine, and [14C]oleic acid into their lipids. The microscopic image of the isolated transport components revealed a population of 80- to 100-nm vesicles with occasional membranes of the ER used for their synthesis. On the average, the vesicles contained 82 ng apomucin/μg of protein and 80–90% of the total incorporated lipid precursors. From that, 91% of [14C]choline was detected in phosphatidylcholine, and 9% in phosphatidylethanolamine, lysophosphatidylcholine, and sphingomyelin. With [14C]oleate, 54% of the label was incorporated into ceramide, diglyceride, and phosphatidic acid, 35% to phosphatidylcholine, 7% in phosphatidylethanolamine, and 2% in sphingomyelin. After incubation of the vesicles with Golgi, the apomucin was found glycosylated and the lipids of the transport vesicles incorporated into Golgi membranes. The fusion of the vesicular membranes was accompanied by the synthesis of sphingomyelin. In the Golgi, 39–55% of the radiolabeled phosphatidylcholine of transport vesicles was converted to sphingomyelin. The results indicate that the newly synthesized membranes of apomucin transporting vesicles are enriched in phosphoglycerides and ceramides. Upon fusion with the Golgi, the membranes of the vesicles are replenished with sphingomyelin by exchange reaction between phosphatidylcholine and ceramide.
    Archives of Biochemistry and Biophysics 10/1992; 298(1):167-175. DOI:10.1016/0003-9861(92)90108-9 · 3.04 Impact Factor
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    ABSTRACT: 1. Analysis of the submandibular saliva revealed that the secretion consists of mucin complexed with 150 kDa fibronectin fragment and DNA. 2. The kallikreins, secreted by the submandibular gland, appear to be responsible for the fibronectin fragmentation, since an identical peptide was also generated when fibronectin was subjected to incubation with the submandibular saliva or the purified enzyme. 3. The results provide evidence that the 150 kDa glycopeptide so-called salivary mucin "link" component is neither an integral part of the mucin molecule, nor linked to mucin subunits by disulfide bonds, but is a fibronectin fragment which associates with mucin. 4. Using mucin monoclonal antibody (3G12), it was revealed that the nonglycosylated (naked) 8-12 kDa fragment of the mucin molecule is responsible for the interaction of mucin with other components of saliva. 5. Under physiological conditions, the interaction of mucin with fibronectin on the luminal surfaces may be relevant in building mucous barrier and protection of the delicate oral epithelium from damage.
    International Journal of Biochemistry 07/1992; 24(6):1003-15. DOI:10.1016/0020-711X(92)90111-D · 4.24 Impact Factor
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    ABSTRACT: The effect of prolonged administration of an antiulcer drug, sofalcone, on the physicochemical properties of gastric mucus was investigated. The experiments were conducted with two groups of rats in which one group received a dose of 100 mg/kg of sofalcone twice daily for three consecutive days, and the control group received daily doses of vehicle. The rats were killed 16 h after the last dose, their stomachs dissected, and the mucosa subjected to physicochemical measurements. The results revealed that sofalcone evoked a 23% increase in mucus gel thickness, and its content of sulfo- and sialomucins increased by 54 and 25%, respectively. These changes in mucus with sofalcone were accompanied by a 16% increase in H+ retardation capacity, twofold increase in viscosity, and a 39% increase in the gel hydrophobicity. The mucus elaborated in the presence of sofalcone exhibited a 10% lower content of protein, 30% higher content of carbohydrate, and 18% higher content of total lipids, which were particularly enriched (20%) in phospholipids and contained 67% more covalently bound fatty acids. Furthermore, the high molecular weight mucus glycoprotein form accounted for about 30% of gel mucin in the control group, whereas its content in mucus gel of animals receiving sofalcone reached 50%. The results indicate that sofalcone enhances the protective qualities of the mucus component of the gastric mucosal barrier and hence strengthens the gastric mucosal integrity.
    Journal of Clinical Gastroenterology 02/1992; 14 Suppl 1:S88-93. DOI:10.1097/00004836-199206001-00015 · 3.19 Impact Factor
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    ABSTRACT: The effect of prolonged administration of an antiulcer drug, sofalcone, on the physicochemical properties of gastric mucus was investigated. The experiments were conducted with groups of rats receiving twice daily for three consecutive days a dose of 100 mg/kg sofalcone, while the control group received daily doses of vehicle. The rats were sacrificed 16 h after the last dose and gastric mucosa subjected to physicochemical measurements. The results revealed that sofalcone evoked a 23% increase in mucus gel dimension, while sulfo- and sialomucins content of the gel increased by 54 and 25%, respectively. These changes were accompanied by a 16% increase in mucus H+ retardation capacity, 2-fold increase in viscosity, and a 39% increase in the gel hydrophobicity. The mucus elaborated in the presence of sofalcone contained 67% more covalently bound fatty acids, exhibited 10% lower content of protein, 30% higher content of carbohydrate, and 18% higher content of lipids. The mucus of the sofalcone group also showed an increase in the proportion of the high molecular weight mucus glycoprotein form, which in the control group accounted for about 30% of gel mucin, while its content in mucus gel of animals receiving sofalcone reached the value of 50%. The results indicate that sofalcone enhances the protective qualities of mucus component of gastric mucosal barrier.
    Journal of physiology and pharmacology: an official journal of the Polish Physiological Society 10/1991; 42(3):293-304. · 2.72 Impact Factor
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    ABSTRACT: The effects of intragastric administration of sucralfate on the physicochemical properties of gastric mucus, and the mechanism of its protective action against alcohol-induced mucosal injury were investigated using in vivo and in vitro models. The experiments in vivo were conducted with groups of rats receiving a dose of 100 mg sucralfate twice daily for 5 consecutive days. The animals were sacrificed 16 hours after the last dose, their stomachs dissected, and the mucosa subjected to physicochemical measurements. In the in vitro studies, gastric mucosa was cultured in the presence of sucralfate, ethanol, or both. The in vivo results revealed that sucralfate elicited an 8% increase in mucus gel dimension, while its sulfo- and sialomucin content increased by 63% and 81%, respectively. The changes in mucus gel mucin content with sucralfate were accompanied by a 9.5% increase in mucus hydrogen ion (H+) retardation capacity, 1.9-fold increase in viscosity, and a 60% increase in the gel hydrophobicity. The mucus elaborated in the presence of sucralfate exhibited 14% lower protein content and 62% higher content of carbohydrate than that of control, and contained more neutral lipids. Furthermore, the gastric mucus of the sucralfate group showed a marked increase in mucus glycoprotein polymeric form. The data obtained with gastric mucosal culture demonstrated that sucralfate elicited a significant increase in mucin synthesis, which was reflected in the enhanced metabolism of mucosal phosphoinositides. In contrast, ethanol, which exhibited detrimental effects on mucin synthesis, also caused alterations in the phosphoinositide signal pathway. The changes in mucin and phosphoinositide distribution patterns evoked by ethanol were prevented by sucralfate. Our results suggest that the mucosal strengthening action of sucralfate occurs through the stimulation of the metabolism of phosphoinositide-derived messenger molecules.
    The American Journal of Medicine 09/1991; 91(2A):30S-36S. DOI:10.1016/0002-9343(91)90448-7 · 5.30 Impact Factor
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    ABSTRACT: Human and rat intestinal mucin was purified by equilibrium density gradient centrifugation and Sepharose 2B chromatography according to M. Mantle, D. Mantle, and A. Allen (1981, Biochem. J. 195, 277-285) and analyzed using mucin, DNA, and fibronectin-specific antibodies in dot-blot, ELISA, and Western blotting. The 118-kDa component of the mucins and the 118-kDa fragment of fibronectin from the same source displayed affinity for concanavalin A and immunoreacted with fibronectin antibodies. The amino acid and carbohydrate compositions of the 118-kDa peptide electroeluted by gel electrophoresis of mucin and fibronectin preparations were identical within each pair of glycopeptides and closely resembled the "link protein component" of human and rat intestinal mucin preparations of R. E. F. Fahim, R. D. Specian, G. G. Forstner, and J. F. Forstner (1987, Biochem. J. 243, 631-640) and M. Mantle and G. Stewart (1989, Biochem. J. 259, 631-640). We therefore conclude that the "link protein" claimed to be an integral part of mucus glycoproteins in actuality is the 118-kDa fragment of fibronectin.
    Archives of Biochemistry and Biophysics 06/1991; 286(2):383-8. DOI:10.1016/0003-9861(91)90055-N · 3.04 Impact Factor
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    ABSTRACT: 1. The mechanism of gastric mucosal protection by an anticular agent, nitecapone, against injury was investigated in rats with and without indomethacin pretreatment. 2. Animals received intragastrically either a dose of nitecapone or vehicle alone, followed by ethanol given at various intervals up to 5 hr, and their gastric mucosa subjected to histologic and physicochemical assessment. 3. Ethanol caused extensive gastric hemorrhagic lesions which were essentially prevented by nitecapone at doses of 30 mg and higher per kg body weight. The maximal protection was achieved by 1.5 hr which persisted up to 4 hr and was not thwarted by indomethacin. 4. Physicochemical measurements revealed that nitecapone evoked 78% increase in mucus gel dimension, and showed 21% increase in phospholipids, and the content of sulfo-(22%) and sialomucins (72%). This was accompanied by 1.6-fold increase in mucus viscosity, 31% increase in H+ retardation capacity and 2.2-fold increase in hydrophobicity. 5. The results suggest that the gastroprotective action of nitecapone occurs through the enhancement of the physicochemical characteristics of mucus layer.
    General Pharmacology 02/1991; 22(6):1055-62. DOI:10.1016/0306-3623(91)90577-S