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G Nardone

Publications and source records attributed to G Nardone.

At least 55 records · Page 3Linked to original sources
PubMed1993

Phospholipid composition of human gastric mucosa: a study of endoscopic biopsy specimens.

Gastric mucosal phospholipids, and in particular those of the surface layer, play an important part in mucosal barrier function. This study examined whether the phospholipid composition of the full thickness gastric mucosa is changed in peptic ulcer disease and gastritis. The phospholipid composition of gastric mucosa from endoscopic biopsy specimens in 28 subjects (eight healthy controls, 12 patients with duodenal ulcer, and eight with chronic atrophic gastritis) was studied. In addition, the phospholipid composition of gastric mucosa was compared with that of duodenal mucosa in 10 patients with duodenal ulcer. As expected phosphatidylcholine and phosphatidylethanolamine prevailed in all three groups. Lysolecithin was the smallest component in the duodenal ulcer and chronic atrophic gastritis groups. The phosphatidylethanolamine value was higher in duodenal ulcer and lower in chronic atrophic gastritis compared with the control group. In chronic atrophic gastritis there was an appreciable amount of phosphatidylglycerol that was not present in patients with duodenal ulcer or in the control group. There was no significant difference in phospholipid composition between antral and duodenal sites in duodenal ulcer patients. In conclusion, the phospholipid composition of gastric mucosa changes in human gastrointestinal diseases but its relation to cellular functions needs further study.

Adult↗
PubMed1992

Hyperuricemia induced by fructose load in liver cirrhosis.

The intravenous administration of fructose in healthy subjects may induce an increase of blood uric acid and the urinary excretion of urate and xanthine as a result of hepatic adenosine triphosphate (ATP) breakdown. These changes are partially reversed by ATP resynthesis. We studied the effect of fructose load (0.5 g/kg body weight) on the products of ATP metabolism, and the interference of fructose on the galactose test in 10 patients with well compensated cirrhosis compared with 10 healthy controls. The fructose and the fructose/galactose loads induced a significantly greater increase of plasma uric acid in cirrhotics than in controls, with a 60 minute peak in the cirrhotics. Urinary excretion of urate and xanthines was significantly increased (p less than 0.001) only in the cirrhotics after the fructose/galactose load. As expected, the galactose elimination capacity (GEC) calculated with the galactose test, was lower in these patients than in controls. Fructose infusion before galactose did not significantly modify the GEC in either of the two groups compared. The higher uric acid increase induced by fructose in the blood of cirrhotic patients seems to be a good marker of the energy crisis of the diseased liver whereby it is unable to efficiently resynthesize ATP from its breakdown products.

Adult↗
PubMed1990

The time-resolved kinetics of superhelical DNA cleavage by BamHI restriction endonuclease.

The kinetics of the cleavage of superhelical plasmid DNA (pBR322) by the restriction endonuclease, BamHI, have been analyzed in terms a compartmental model consistent with the chemistry first proposed by Rubin and Modrich (Rubin, R. A., and Modrich, P. (1978) Nucleic Acids Res. 5, 2991-2997) for analysis of the kinetics of the restriction endonuclease, EcoRI. The model was defined in terms of two compartments representing DNA substrate (bound and free), two compartments representing nicked intermediate (bound and free), one compartment representing linear product, and one compartment for free enzyme. A simultaneous analysis of concentration changes over time of the three DNA forms (superhelical, nicked, and linear) at six different enzyme concentrations was undertaken employing this compartmental model using SAAM (Simulation Analysis And Modeling) software. Results showed that rate constants characterizing the association of enzyme with superhelical DNA (6.0 x 10(5) M-1 s-1) and nicked DNA (2.8 x 10(5) M-1 s-1) were similar in magnitude and rate constants characterizing cleavage of the first (1.2 x 10(-2) s-1) and second phosphodiester bonds (3.1 x 10(-2) s-1) were also similar. The analysis yields a kinetically determined equilibrium constant of 12.9 nM for the dissociation of nicked intermediate from the enzyme. The rate constant describing the release of the nicked intermediate from the enzyme has a value of 3.7 x 10(-3) s-1. By comparing the value of this release rate constant to the value of the constant describing the second cleavage event, it can be determined that only 10% of the nicked intermediate bound to the enzyme is released as free nicked DNA and that 90% of the nicked intermediate is processed to the linear form without being released. Hence, most of the DNA is cleaved as the result of a single enzyme-DNA recognition event. No steady state assumptions were made in the analysis. The approach was to directly solve the differential equations which described the kinetic processes using an interactive method. This study demonstrates the usefulness of this approach for the analysis of kinetics of protein-DNA interactions for the restriction endonucleases.

DNA, Superhelical↗
PubMed1990

DNA structural polymorphism modulates the kinetics of superhelical DNA cleavage by BamHI restriction endonuclease.

A compartmental model developed by Hensley (Hensley, P., Nardone, G., Chirikjian, J.G., and Wastney, M. E., (1990) J. Biol. Chem. 265, 15300-15307) for analysis of the time courses of the cleavage of superhelical DNA substrates by the restriction endonuclease, BamHI, has been used to quantify the effects of changes in temperature, ionic strength, superhelical density, and the DNA substrate on the binding and strand cleavage processes. Studies reported here indicate that changes in topology may be introduced into the DNA substrate solely as a result of the plasmid preparation process and in the absence of covalent bond cleavage and ligation. These changes in topology have qualitatively different effects on the kinetics than those promoted by changes in the superhelical density. The former are removed by briefly warming the DNA prior to assay, suggesting that they are only kinetically stable, while the latter changes are not affected by heating. Increasing the [NaCl] from 0.01 M to 0.1 M increases the overall rate of plasmid cleavage by increasing both the rates of cleavage and enzyme DNA association. To describe the decrease in the overall cleavage rate observed in 0.15 M NaCl, an ionic strength-dependent rate-determining structural transition in the DNA substrate was incorporated into the model. The largest changes in the rate of the cleavage process resulted from changes in the DNA substrate. For the SV40 substrate compared to pBR322, the rate constants describing the two association processes and the first bond cleavage event were increased 6- to 7-fold. The rate of the second bond cleavage process was not affected. These changes may be due to differences in the flanking sequences.

DNA, Superhelical↗
PubMed1990

Adult Fanconi syndrome and liver cirrhosis.

A female presenting primary adult Fanconi syndrome and liver cirrhosis of obscure aetiology is described. The only other report of this association appeared over four decades ago and concerned a male patient who, however, was subsequently diagnosed as having Wilson's cirrhosis, a well-known cause of acquired Fanconi syndrome. Therefore, the present report is the first account of primary Fanconi syndrome with authentic cryptogenic liver cirrhosis. Since the chronic urinary amino acid leakage is not a pathogenetic mechanism of the cirrhotic process, we believe that this association in fortuitous.

Fanconi Syndrome↗
PubMed1989

On a rare atypical form of metachromatic leukodystrophy (MLD): "neurological non-mld patients with low levels of arylsulphatase A". Description of two cases.

Two young patients (a brother and his sister) with low ASA levels who had myoclonic seizures since the age of eight years, were investigated by means of electrophysiological, neuroradiological and laboratory tests and submitted to a physical examination. In both patients, the disease started at the age of eight years with drug resistent myoclonic seizures. Intelligence was not impaired and ASA levels were lower than normal, but clinical features were not those of classic MLD. Electrophysiological study revealed altered SEPs and normal BAEPs (they are both altered in leukodystrophy). Therefore our findings conclude that tour patients must be considered "Neurological patients non-MLD with low levels of ASA".

Adolescent↗
PubMed1987

Investigation of intestine function during acute viral hepatitis using combined sugar oral loads.

One fifth of all cases of A virus hepatitis (AVH) have symptoms of gastroenteritis at the onset. This study investigated the mediated intestinal absorption of D-xylose (D-xyl) and 3-o-methyl-D-glucose (3-omG) and the non-mediated permeation of lactulose (Lacl, mol wt 342) and L-rhamnose (L-rh, mol wt 164) during acute and remission phases of AVH. Ten patients with AVH were given an oral load containing these sugars (5 g D-xyl: 2.5 g 3-omG, 1 g L-rh, 5 g lacl in 250 ml water) once during the acute phase and again during remission. The same load was given once to a group of 22 healthy controls. The mean concentration of D-xyl in urine and the ratio of D-xyl to 3-omG in plasma and urine were normal in both the AVH phases, ruling out intestinal malabsorption even in the acute phase. This study showed a significant increase in non-mediated permeation to Lacl, but not to L-rh, during the acute phase. These data indicate that the barrier function of the intestine is compromised in AVH infection while the absorptive function is not. An abnormally low concentration of D-xyl and 3-omG in plasma at one hour was found in all patients during the acute phase. This finding cannot be explained by alterations in intestinal absorption, but could be accounted for by increased space distribution of the sugars because of increased diffusion into tissue cells and/or expansion of the extracellular space by fluid retention.

3-O-Methylglucose↗
PubMed1986

Differences in the kinetic properties of BamHI endonuclease and methylase with linear DNA substrates.

BamHI endonuclease and methylase were found to exhibit a kinetic preference for linear pBR322 DNA substrates containing the recognition site in a central location. The Km values for substrates having the recognition site in a terminal location were approximately 3-fold greater than those with a centrally located site. This phenomenon may be partially due to facilitated transfer of the enzymes to the recognition site over nonspecific flanking sequences. The exploitation of facilitated transfer by these enzymes has been inferred from studies demonstrating kinetic preferences for longer DNA substrates. The reaction rates of the endonuclease were 9-fold greater with full-length pBR322 DNA than with a 74-base pair derivative. The methylase exhibits a kinetic preference for longer substrates but only under conditions of comparatively higher DNA concentrations. In addition, the methylase has the property of increasing long chain preference with increasing salt concentrations up to 120 mM. Increasing salt concentrations decreased the endonuclease's preference for longer substrates. Nonspecific inhibition studies revealed qualitative and quantitative differences between the two enzymes under catalytic conditions. These studies suggest that BamHI endonuclease and methylase interact with nonspecific DNA in different ways.

DNA (Cytosine-5-)-Methyltransferases↗
PubMed1985

Sequence-specific BamHI endonuclease. The proposed role of arginine residues in substrate binding and recognition.

Arginyl residues in BamHI endonuclease were examined because of their alleged role in proteins that contain nucleotide- or phosphate-binding sites. Butanedione, an arginine-specific reagent, inhibited the endonuclease in the presence of sodium borate. The inhibition was decreased by preliminary incubation of the enzyme with DNA or competitive inhibitors which were the 5'-phosphoryl deoxydinucleotide subsets of the BamHI recognition sequence. The dinucleotide pdGpdG protected the enzyme most efficiently against the butanedione modification. Dinucleotides that were unrelated to the recognition sequence failed to protect the enzyme from inactivation. These studies indicate that arginine residues may reside in the enzyme's active site and might function in the sequence-specific recognition of the BamHI palindrome.

Arginine↗
PubMed1984

Sequence-specific BamHI methylase. Purification and characterization.

BamHI methylase has been purified to apparent homogeneity. The isolated form of the enzyme is a single polypeptide with a molecular weight of 56,000 as determined by sodium dodecyl sulfate-polyacrylamide electrophoresis. Unlike BamHI endonuclease, which is isolated as a dimer and higher aggregates, the methylase has no apparent higher form. The methylase requires S-adenosyl-L-methionine as the methyl-group donor and is inhibited by Mg2+. The enzyme is also inhibited by 2,3-butanedione and reagents specific for sulfhydryl groups, such as N-ethylmaleimide, which suggests a role for arginine and cysteine residues, respectively. DNA efficiently protects the enzyme against the butanedione modification while S-adenosylmethionine has no effect. In contrast, S-adenosylmethionine protects against cysteine modification while DNA produces only small amounts of protection. Studies on the mechanism of methylation indicate that both strands of the recognition sequence are modified in a single binding event. The sequence specificity of the methylase is relaxed upon the addition of glycerol in the reaction mixture. In the presence of 30% glycerol the enzyme methylates sequences that are also recognized by BamHI endonuclease when acting under conditions of relaxed specificity.

Bacillus↗
PubMed1983

[Blood amino acids in chronic HBsAg positive liver disease].

Typical changes in blood aminoacid concentrations have been described in patients with severe liver disease. In this study we measured the serum amino acid levels, by Beckman Aminoacid Analyzer, in 11 healthy subjects and 24 HBsAg-positive patients with biopsy-proven liver disease (4 CPH, 10 CAH, 10 cirrhosis). A significant decrease in total aminoacids was observed in CAH and cirrhosis groups (-24% and -22% respectively). The three branched chain aminoacids (BCAA = val + leu + isoleu) were reduced by 24% (P less than 0.002) and 37% (P less than 0.001) in the CAH and cirrhosis groups respectively. Tyrosine was the only of the aromatic aminoacids (AAA) to increase in cirrhotics (+ 34%, P less than 0.02). The molar ratio BCAA/AAA was 3.6 in controls, 3.8 in CPH, 3.1 in CAH (P less than 0.025) and 1.9 in cirrhosis (P less than 0.001). A linear correlation was found between molar ratio BCAA/AAA and serum albumin in all patients (P less than 0.001). These results document the presence of specific quantitative changes in serum aminoacids of HBsAg positive patients, which appear related to severity of liver disease and comparable to the alterations described in non viral chronic liver disease.

Adolescent↗