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Biomedical subjects

R Carubelli

Publications and source records attributed to R Carubelli.

At least 37 records · Page 2Linked to original sources
PubMed1983

Respiratory mucous secretions in patients with cystic fibrosis: relationship between levels of highly sulfated mucin component and severity of the disease.

The tracheobronchial secretions from cystic fibrosis patients contained higher levels of protein, DNA and sialic acid than the tracheobronchial secretions from healthy donors. In contrast, the neutral hexose content in CF secretions was strikingly lower than in secretions from normal subjects. The levels of neutral hexose and sialic acid in the CF secretions were found to increase with increasing severity of the disease. The alterations in the levels of these chemical parameters in the secretions of patients with increased disease severity are as a result of increased levels of the mucin content of the secretions, especially of the highly sulfated mucin component. Since mucins are considered, to a large extent, responsible for the viscoelastic properties of the secretions, the enhanced levels of the highly sulfated mucin component in the secretions of the patients with increased disease severity, may contribute to altered rheological properties and hence decreased mucociliary transport of the secretions.

Cystic Fibrosis↗
PubMed1982

Sialic acid metabolism in rats undergoing chemically induced hepatocarcinogenesis in specific dietary states.

The sialic acid content and the activities of the enzymes responsible for the activation, transfer, and hydrolysis of sialic acid were determined in the livers of male Sprague-Dawley rats maintained on diets containing the hepatocarcinogen 2-acetylaminofluorene (AAF). The incidence of hyperplastic lesions was modulated by dietary fat and by the presence of a synthetic antioxidant. The purified diets utilized differed in the amount and degree of unsaturation of the lipid component; they contained either 20% corn oil, 18% coconut oil + 2% linoleic acid, or only 2% linoleic acid, and each diet was prepared either with or without 0.3% butylated hydroxytoluene (BHT). The supplementation of diets with BHT greatly retarded the development of hyperplastic nodules compared to unsupplemented diets. The AAF-treated rats and age-matched controls fed AAF-free diets were killed after a 12 to 17-week period of dietary treatment, and the livers were removed for histological and biochemical studies. Significant increases in sialic acid content, and in the activities of CMP-sialic acid synthetase and neuraminidase were observed in the livers from AAF-treated rats. The BHT supplementation of the AAF-containing diets resulted in livers with lower levels of sialic acid and CMP-sialic acid synthetase activities. The chemical and enzymatic changes observed in AAF-treated rats are consistent with an increased turnover of sialoglycoconjugates during the carcinogenic process.

2-Acetylaminofluorene↗
PubMed1981

Sialic acid metabolism in regenerating rat liver.

Sialic acid metabolism was investigated in control rat liver, in regenerating liver at 24 h and 48 h after partial hepatectomy and in the liver of sham-operated animals. High levels of membrane-bound neuraminidase, with no detectable changes in the soluble enzyme, were observed in regenerating rat liver. The neuraminidase activities in the liver of sham-operated rats were identical to those present in control liver. High levels of CMP-N-acetylneuraminic acid synthetase and sialyltransferase were observed both in regenerating liver as well as in the liver of sham-operated rats. The sialic acid content of regenerating rat liver, which was lower than that found in the liver of control and sham-operated rats at 24 h, returned to normal values 48 h after surgery.

Animals↗
PubMed1979

Hydrophobic interaction of fluorescent probes with fetuin, ovine submaxillary mucin, and canine tracheal mucins.

The presence of hydrophobic sites in fetuin, ovine submaxillary mucin and two homogeneous canine tracheal mucins was established by fluorescence probe techniques. The interaction between the above-mentioned glycoproteins and two hydrophobic fluorescent compounds, sodium mansate and mansylphenylalanine, was accompanied by an enhancement in fluorescence and a shift of the fluorescence maxima to shorter wavelengths. The introduction of a phenylalanine residue to the mansyl group enhanced the binding affinity of the probe for the hydrophobic sites of these glycoproteins as evidenced by lower values for the dissociation constants. The high molecular weight (581 600) tracheal mucin, which had the highest carbohydrate content (80%) of all the glycoproteins investigated, exhibited the highest fluorescence enhancement and the largest number of binding sites for these fluorescent probes.

Animals↗
PubMed1979

Sialic acid metabolism in rats undergoing chemically-induced mammary gland carcinogenesis in specific dietary states.

The enzymes responsible for the activation, transfer and hydrolysis of sialic acids were investigated in female rats with mammary adenocarcinomas induced by administration of a single oral dose (10 mg) of 7,12-dimethylbenz[alpha]anthracene. The carcinogenic process was modulated by the levels and degree of unsaturation of the dietary lipids. Tumor incidence was highest in rats fed a diet containing 20% corn oil, intermediate with 18% coconut oil plus 2% linoleic acid, and lowest in the group receiving a diet with 2% linoleic acid. Sialyltransferase and CMP-N-acetylneuraminic acid synthetase activities were higher in tumors than in control mammary glands. Neuraminidase activity, on the other hand, was higher in control tissue than in tumors. In addition to these tumor-related effects, comparison of the enzyme levels in mammary tissues from control animals of the 3 dietary groups revealed the presence of diet-related effects on sialic acid metabolism. In the livers of tumor-bearing rats, only minor changes of enzyme activities were detected.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1979

Urinary metabolite of 1-(2,4,6-trichlorophenyl)-3,3-dimethyltriazene with an intact diazoamino structure.

The tumour-inhibiting substance 1-(2,4,6-trichlorophenyl)-3,3-dimethyltriazene is metabolised in rats to the corresponding substituted 1-O-(triazenyl-methyl) glucuronic acid. The urinary metabolite was purified by ion exchange chromatography and gel filtration, and isolated from the enriched fractions by freeze-drying. Cold acid cleavage into the 2,4,6-trichlorobenzene-diazonium cation and hydrolysis to glucuronic acid and formaldehyde indicated the presence of an O-glycosidic bond through an enzymically-introduced hydroxymethyl oxygen. This novel type of glucuronoside structure was established by chemical evidence, and confirmed by NMR and field-desorption mass spectrometry. It is conceivable that this metabolite represents a stabilised carrier form of the biologically-active triazene that transports the methylating agent from its site of formation to its ultimate target.

Animals↗
PubMed1978

Studies of erythrocyte sequestration. II. Liver homing.

Xenogeneic and enzyme-treated erythrocytes rapidly home to the rat liver as measured by scintigraphic procedures. Histology and scanning electron microscopy revealed that pronase digested erythrocytes are taken up as whole cells by liver histiocytes.

Animals↗
PubMed1978

Isolation and characterization of glycoproteins from canine tracheal mucus.

Three homogeneous glycoproteins were isolated from reduced and S-carboxy-methylated canine tracheal pouch mucus by gel filtration and ion-exchange chromatography. Initial fractionation was carried out on Sephadex G-200; chromatography of the excluded Sephadex G-200 fraction on Bio-Gel A-15 m yielded two high molecular weight glycoprotein fractions. Following rechromatography on the same column, the main fraction behaved as an electrophoretically homogeneous high molecular weight (581 600) glycoprotein, with a high carbohydrate content (80%) and a single amino-terminal amino acid (arginine). Ion-exchange chromatography (DEAE-cellulose) of the included Sephadex G-200 fraction yielded two electrophoretically homogeneous glycoproteins of lower molecular weight (20 800 and 24 600, respectively). A single amino-terminal amino acid, glycine and alanine, respectively, was detected for each glycoprotein. Chemical analysis of these three glycoproteins revealed the presence of fucose, galactose, N-acetylgalactosamine, N-acetylglucosamine, N-acetylneuraminic acid and sulfate monoester. The high molecular weight glycoprotein had a higher hexose, sialic acid and sulfate content, per mg of protein, than the low molecular weight glycoproteins. The results of the alkaline borohydride treatment indicated that the majority of the carbohydrate chains of these glycoproteins are linked to the protein core through O-glycosidic bonds involving N-acetylgalactosamine and serine or threonine.

Amino Acids↗
PubMed1977

Effect of acute ethanolic intoxication on the neuraminidase activity of rat liver Golgi apparatus.

Neuraminidase and galactosyltransferase were investigated in total Golgi appartus and in the three fractions of increasing densities (GF1, GF2, and GF3) isolated from the microsomal fraction of rat liver homogenates by flotation in a discontinuous sucrose density gradient (Ehrenreich, J.H., Bergeron, J.J.M., Siekevitz, P. and Palade, G.E. (1973) J. Cell Biol. 59, 45-72). About 50% decreases in neuraminidase content (units/g liver) and specific activity (units/mg protein) were observed in total Golgi as well as in the three fractions isolated at 45 min, 90 min, 180 min and 16 h after administration of a single oral dose of 50% aqueous ethanol (0.6 g/100 g body weight). Colchicine administration (introperitoneal injection, 0.5 mg/100 g body weight) caused a similar loss of neuraminidase activity; however, the effect of ethanol plus colchicine was not additive. Golgi galactosyltransferase, on the other hand, experienced marked increases of activity following ethanol administration but, unlike the results reported by others (Gang, H., Lieber, C.S. and Rubin, E. (1973) Nat. New Biol. 243, 123-125), significant increases in total activity and specific activity were already quite evident at 90 min after ethanol ingestion. In contrast with the decreased values observed in Golgi, the total particle-bound neuraminidase was significantly elevated following ethanol administration. Ultrastructural studies revealed increased lysosomal content and detachment of polysomes from the rough endoplasmic reticulum. A model, which takes into account these enzymological and ultrastructural findings and their biological significance, is proposed.

Animals↗
PubMed1976

Interaction between the soluble and particulate neuraminidases of chick liver.

The sum of the neuraminidase activities found in the isolated soluble and particulate fractions of chick liver was considerably higher than that observed in the cytoplasmic extract from which these fractions were obtained. Addition of increasing amounts of particulate neuraminidase to a constant amount of the soluble preparation resulted in a progressive loss of enzyme activity.

Animals↗
PubMed1975

Membrane-bound neuraminidases of rat liver. Neuraminidase activity in Golgi apparatus.

The bulk (60 to 65%) of the neuraminidase activity present in rat liver homogenates was found in the M + L (mitochondria plus lysosomes) fraction, The patterns of subcellular distribution were essentially identical whether disialogangliosides or neuramin-lactose (2 yields 3') were utilized as substrates. A new neuraminidase, which hydrolyzes sialyl trisaccharides but which does not act upon glycoproteins and gangliosides, was detected in Golgi apparatus. Unlike the other particulate neuraminidases of rat liver, the Golgi enzyme is stimulated by prior incubation and by the addition of Ca2+ or Zn2+ at 1 mM concentration. Although plasma membrane-rich fractions are often contaminated by Golgi membranes the marked differences in their enzymic properties allowed a clear distinction between the neuraminidases present in these two types of membranes.

Animals↗