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G Magni

Publications and source records attributed to G Magni.

At least 55 records · Page 3Linked to original sources
PubMed1997

Characterization of nicotinamide mononucleotide adenylyltransferase from thermophilic archaea.

The enzyme nicotinamide mononucleotide (NMN) adenylyltransferase (EC 2.7.7.1) catalyzes the synthesis of NAD+ and nicotinic acid adenine dinucleotide. It has been purified to homogeneity from cellular extracts of the thermophilic archaeon Sulfolobus solfataricus. Through a database search, a highly significant match was found between its N-terminal sequence and a hypothetical protein coded by the thermophilic archaeon Methanococcus jannaschii MJ0541 open reading frame (GenBank accession no. U67503). The MJ0541 gene was isolated, cloned into a T7-based vector, and expressed in Escherichia coli cells, yielding a high level of thermophilic NMN adenylyltransferase activity. The expressed protein was purified to homogeneity by a single-step chromatographic procedure. Both the subunit molecular mass and the N-terminal sequence of the pure recombinant protein were as expected from the deduced amino acid sequence of the MJ0541 open reading frame-encoded protein. Molecular and kinetic properties of the enzymes from both archaea are reported and compared with those already known for the mesophilic eukaryotic NMN adenylyltransferase.

Amino Acid Sequence↗
PubMed1996

Three-minute high-performance liquid chromatographic assay for NMN adenylyltransferase using a 20-mm-long reversed-phase column.

NMN adenylyltransferase (NAD pyrophosphorylase; NMNAT) reversibly catalyzes the synthesis of NAD from ATP and NMN. In this paper, we describe a rapid and sensitive high-performance liquid chromatographic assay for NMNAT, which uses a 20-mm-long C18 reversed-phase (RP) column. The activity was measured by separating in less than 3 min the substrates (NMN and ATP) from the product (NAD) with 0.1 M potassium phosphate, pH 6.0, at a 2 ml/min flow-rate and 22 degrees C. NAD was directly quantitated from its ultraviolet absorbance. Amounts of NAD as small as 25 pmol could be measured. The activity value closely agreed with that determined by the spectrophotometric assay. This method was successfully applied to the determination of NMNAT activity in human placental and bull testis extracts, as well as in rat pheochromocytoma (PC12) cells.

Adult↗
PubMed1996

Effects of angiotensin-converting enzyme inhibition on left ventricular geometric patterns in patients with essential hypertension.

Although angiotensin-converting enzyme inhibitors have been shown to affect left ventricular (LV) remodeling favorably in several conditions, it remains unclear whether they can influence LV geometric pattern in hypertension. To address this issue, 122 patients (71 men and 51 women; mean age = 51 +/- 10 years) with mild to moderate hypertension were studied prospectively. All underwent clinical evaluation and Doppler echocardiography at entry and more than 2 years of quinapril therapy (10-40 mg/day). According to either LV mass (normal if < 131 g/m2 for men or < 100 g/m2 for women) or the ratio of LV posterior wall thickness to diastolic diameter (RWT; normal if < 0.45) at baseline, 58 patients had normal mass and RWT, 18 patients had concentric remodelling (i.e., normal mass but increased RWT), 24 patients had eccentric hypertrophy (i.e., increased mass but normal RWT), and 22 patients had concentric hypertrophy (i.e., increase in both mass and RWT). After 6 months of quinapril therapy, all patients with normal left ventricles showed the maintenance of mass and RWT within normal limits. Patients with concentric remodeling showed no increase in mass but had a significant decrease in RWT. Patients with eccentric hypertrophy exhibited a significant reduction in mass with no substantial change in RWT. Patients with concentric hypertrophy had a significant reduction in both mass and RWT. Changes in LV mass and geometry were maintained during the 2-year period of treatment and were paralleled by improvements in Doppler indices of LV diastolic function in each group. It is concluded that quinapril, with its well-known effects on LV hypertrophy, modifies the LV geometric pattern of hypertensive patients favorably, regardless of the presence of an abnormal LV mass or RWT.

Adult↗
PubMed1996

Volume-rendered, three-dimensional echocardiographic determination of the size, shape, and position of atrial septal defects: validation in an in vitro model.

Accurate evaluation of atrial septal defect (ASD) size and shape is very important for the selection of patients for transcatheter occlusion. The ability of volume-rendered, three-dimensional echocardiography (3DE) in displaying ASDs in a dynamic mode has been demonstrated; however, its accuracy in sizing ASDs is unknown. To assess this, we performed 3DE of 10 explanted pig hearts in which ASDs of various locations, sizes, and shapes had been experimentally created. From en face 3DE views of the atrial septum containing the defects, major and minor diameters of the defect were measured by a blinded observer, and these data were compared to direct anatomic measurements. The correlations between 3DE and anatomy for the major and minor ASD diameters were y = 0.83x + 3.4 (r = 0.97, p < 0.0001) and y = 0.92x + 1.3 (r = 0.92, p < 0.0001) respectively. The correlation between the measures for major and minor axis ratio was y = 1.06 x - 0.052, r = 0.91, p < 0.0002. Good agreement between both methods of measurements was demonstrated for all measurements. In addition, 3DE portrayed the location and shape of the defects accurately. Thus 3DE provides excellent visualization of ASD and is able to accurately define the size of the defects. These qualitative and quantitative capabilities enhance the clinical potential of this technique in the appraisal of ASDs for decisions regarding application of closure devices.

Animals↗
PubMed1996

Malignant cardiac involvement in a family with myotonic dystrophy.

BACKGROUND: In patients with myotonic dystrophy, histopathological and electrophysiologic abnormalities of cardiac conduction system may lead to sudden cardiac death due to atrioventricular block or to ventricular electrical instability. METHODS: Four members of a family affected by myotonic dystrophy are reported, which underwent a cardiological examination including invasive electrophysiological study and prolonged follow-up. Other 3 members of the same family had died suddenly. No clinical data are available for 2 of these patients, while paroxysmal atrial flutter and non sustained ventricular tachycardia had been detected at Holter in the third one. RESULTS: Signs of atrioventricular conduction impairment, poorly predictable with non invasive electrocardiography, were found in the 4 patients undergoing intracardiac electrophysiologic study. In 2/4 patients, both having dizzy spells and the most impaired atrioventricular conduction, a pace-maker was implanted. Polymorphic, non sustained ventricular response was induced in 2/4 patients, 1 of them with spontaneous high grade ventricular arrhythmias. CONCLUSIONS: The respective role of atrioventricular conduction impairment and ventricular vulnerability in determining sudden death has not been stated so far in these patients. The observed polymorphic non sustained response should not be "a priori" disregarded as aspecific, since it could be the electrophysiological counterpart of a peculiar anatomic arrhythmogenic substrate. A comprehensive study, including invasive electrophysiology, is advisable in all patients with myotonic dystrophy whenever a member of their family presents with cardiac involvement, to assess the most probable life-threatening arrhythmogenic mechanism.

Adolescent↗
PubMed1995

NMN adenylyltransferase from bull testis: purification and properties.

The purification procedure of NMN adenylyltransferase from bull testis presented here consists of a heat step and an acidic precipitation followed by four chromatographic steps, including dye ligand, adsorption and hydrophobic chromatography. The final enzyme preparation subjected to non-denaturing and denaturating PAGE with silver nitrate staining exhibited a single band. At this step the enzyme appeared to be homogeneous. The M(r) value of the native enzyme calculated by gel filtration was about 133,000. The protein appeared to possess a quaternary structure with four subunits of apparent M(r) 33,000 without disulphide interchain bonds. Isoelectric experiments gave a pI of 6.2, and pH studies showed the possible presence of an acidic group in the active site having a pKa of 4.9. Analysis of the amino acid composition showed the presence of more acidic residues than basic ones, according to the pI value calculated by Mono P FPLC. The Ea calculated by Arrhenius plot gave an apparent value of 55.7 kJ/mol. The Km values for NMN, ATP, NAD+ and PPi were 0.11, 0.023, 0.37 and 0.16 nM respectively. The polyclonal antiserum produced against the NMN adenylyltransferase reacted with the purified enzyme at different dilutions and recognized the enzyme in the homogenate as well.

Amino Acids↗
PubMed1995

Assay methods for nicotinamide mononucleotide adenylyltransferase of wide applicability.

NMN adenylyltransferase (NMNAT) reversibly catalyzes the synthesis of NAD+ or NaAD+ from ATP and NMN or NaMN. In this work, we describe a continuous coupled spectrophotometric assay that can be rapidly and routinely used in place of the previous cumbersome two-step assay. The reaction rates measured with the coupled assay display a linear dependence with respect to enzyme concentration over the range investigated. The method yields accurate and reliable estimates of the enzyme activity in the direction of NAD+ synthesis. Furthermore, we developed an HPLC-based method suitable for the assay activity both in the forward and reverse directions of the enzymatic reaction. The method appears particularly useful for measuring the NMNAT activity when the product is not NAD+ (e.g., in studies using alternative substrates), and offers the possibility of monitoring simultaneously both the NMNAT-catalyzed reaction and interfering side reactions. This is achieved through the HPLC identification and quantitation of metabolites and derivatives produced in the reaction mixture during the assay. The two methods described here should cover most needs for the assay of NMNAT activity.

Chromatography, High Pressure Liquid↗
PubMed1995

The antitumor drug, 1,3-bis(2-chloroethyl)-1-nitroso-urea, inactivates human nicotinamide mononucleotide adenylyltransferase.

Nicotinamide mononucleotide (NMN) adenylyltransferase (EC 2.7.7.1) from human placenta is rapidly inactivated by 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). A similar inactivation is observed with other C- and N-nitroso compounds. The inactivation by BCNU is dependent on incubation time, temperature and BCNU concentration. Protective reagents for -SH groups, dithiothreitol and beta-mercaptoethanol, and the substrate NMN are very effective in protecting NMN adenylyltransferase from BCNU inactivation and in preserving its catalytic properties, while ATP is less efficient. Incubation of BCNU-inactivated and dialysed NMN adenylyltransferase with dithiothreitol results in a partial recovery of the enzymatic activity.

Adenosine Triphosphate↗
PubMed1995

Effectiveness of venlafaxine in patients hospitalized for major depression and melancholia.

BACKGROUND: This study was undertaken to compare the antidepressant efficacy and short-term safety of venlafaxine with those of placebo in hospitalized patients with major depression and melancholia. METHOD: Ninety-three inpatients with a minimum prestudy Montgomery-Asberg Depression Rating Scale (MADRS) score of 25 were treated for up to 4 weeks with either venlafaxine or placebo. Dosage averaged approximately 350 mg/day during Weeks 2 to 4. Efficacy and safety were assessed throughout the study. Efficacy was evaluated using the MADRS, the 21-item Hamilton Rating Scale for Depression (HAM-D), and the Clinical Global Impressions (CGI) scale. Recorded study events, vital signs and body weight measurements, laboratory determinations, physical examinations, and ECG recordings were used to assess safety. RESULTS: Venlafaxine provided significantly greater improvement in the MADRS scores after 4 days and in the HAM-D scores after 1 week than did placebo. Response rate (based on a 50% decrease in MADRS scores) was 65% (30 of 46 patients) for venlafaxine and 28% (13 of 47 patients) for placebo. Significantly more placebo-treated patients (40%; N = 19) than venlafaxine-treated patients (9%; N = 4) discontinued treatment early because of lack of efficacy. Nausea and sweating were the most common events, occurring at a significantly higher rate in the venlafaxine group. CONCLUSION: Venlafaxine is an effective and well-tolerated antidepressant in hospitalized patients with major depression and melancholia.

Adult↗
PubMed1994

Homogeneous pyrimidine nucleotidase from human erythrocytes: enzymic and molecular properties.

A pyrimidine nucleotidase with unique specificity has been obtained for the first time as an homogeneous protein from the cytosolic fraction of human erythrocytes. Both conventional chromatography and f.p.l.c. techniques have been used in the purification procedure. The final enzyme preparation gave a single protein band of M(r) = 23,500 on SDS/PAGE under both reducing and non-reducing conditions. The native enzyme was eluted at M(r) = 45,000 in gel filtration chromatography on Superose 12, suggesting a dimeric structure. Amino acid analysis was consistent with an acidic isoelectric point and revealed the presence of six half-cystine and two methionine residues per subunit. The enzyme was active on a variety of pyrimidine nucleoside monophosphates, being most active on the 3'-monophosphates. Km values for 3'dUMP, 3'UMP, 5'dUMP, 5'UMP, 5-fluoro-2'dUMP, ranged from 192 microM to 1.15 mM. The enzyme activity was inhibited by both reaction products, orthophosphate, and the nucleoside formed. Product inhibition studies suggested an Ordered Uni-Bi mechanism for the reaction. The enzyme required Mg2+ for its activity, while heavy metals cations were strongly inhibitory. The enzyme activity was inhibited by metal chelating agents and it was sensitive to thioreactive reagents. The isoelectric point was 5.4 and the optimum activity pH was 6.5.

5'-Nucleotidase↗
PubMed1994

Pyridine dinucleotide biosynthesis in archaebacteria: presence of NMN adenylyltransferase in Sulfolobus solfataricus.

The enzyme NMN adenylyltransferase, leading to NAD synthesis, has been observed for the first time in soluble extracts from the extreme acidothermophilic archaeon Sulfolobus solfataricus. Comparison of its molecular and kinetic properties with those of the enzyme isolated from prokaryotes and eukaryotes revealed significant differences, knowledge of which may contribute to the understanding of metabolic evolutionary mechanisms. The thermophilic enzyme shows a molecular mass of about 66,000 and an isoelectric point of 5.4. The Km values for ATP, NMN and nicotinic acid mononucleotide are 0.08 microM, 1.4 microM and 17 microM, respectively. The enzyme shows a remarkable degree of thermophilicity, with an activation energy of 95 kJ/mol.

Adenosine Triphosphate↗
PubMed1994

The role of stressful life events in duodenal ulcer recurrence: a prospective study.

This study prospectively assessed whether stressful life events (LE) were predictive of duodenal ulcer (DU) recurrence during remission of disease. We administered Paykel's Interview for Recent Life Events to 80 patients to assess events that occurred 12 months prior to the first interview and again 6 to 12 months later for LE that occurred during the interval. Upper gastrointestinal endoscopy detected DU recurrence in 11 patients. Prospective data analysis showed no significant difference in LE between relapsing and relapse-free groups, whereas retrospective analysis showed significantly more LE (p > .03) among relapsing patients. LE seems to have played a marginal role in DU recurrence.

Adult↗
PubMed1994

One-minute high-performance liquid chromatography assay for 5'-nucleotidase using a 20-mm reverse-phase column.

A general procedure is described for developing HPLC-based assays for nucleotidases by using a 20-mm C-18 reversed-phase column. The method is applied on the determination of pyrimidine 5'-nucleotidase activity in human erythrocytes lysate and plasma. The activity is detected using isocratic conditions which separate the product (nucleoside) from the substrate (nucleotide) in less than 1 min with 100 mM potassium phosphate, pH 6.0, at a 2 ml/min flow rate. Nucleoside products of the enzymatic reactions are directly quantitated from their ultraviolet absorbances. The activity value closely agreed with that determined by measuring the production of inorganic phosphate. The method does not require prior dialysis of the sample and is 50-fold more sensitive than that based on colorimetric measurements of inorganic phosphate. Furthermore, avoiding the use of radioactive materials offers significant advantages with respect to commonly adopted assays and can be conveniently used for the determination of nucleotidase activity from different sources.

5'-Nucleotidase↗
PubMed1994

Prospective study on the relationship between depressive symptoms and chronic musculoskeletal pain.

Chronic pain and depression often coexist, but there is still uncertainty about the nature of this relationship. Virtually all the available data are cross-sectional and therefore do not clarify the causal relationship between the two variables. In epidemiological studies, chronic pain has often been defined fairly liberally in terms of the actual duration. In this study, the definition of chronic pain was based upon self-reports of pain present for most of the days in at least 1 month of the 12 months preceding the interview. We tested the hypotheses that depression causes pain and that pain causes depression in a sample of 2324 subjects who were assessed for the presence of musculo-skeletal pain and the presence of depression, using for the latter a standardized published instrument called the Center for Epidemiologic Studies Depression scale (CES-D). The subjects were first examined using the National Health and Nutrition Survey (NHANES 1) of the United States National Center for Health Statistics from 1974 to 1975, and were followed-up from 1981 to 1984. Those with data on both occasions represent 76% of an initial population of 3059 persons. On logistic regression analysis depressive symptoms at year 1 significantly predicted the development of chronic musculo-skeletal pain at year 8 with an odds ratio of 2.14 for the depressed subjects compared with the non-depressed subjects. In patients in whom pain was present at baseline no socio-demographic variable alone predicted its persistence; however, male sex and white race together with 2 items of the CES-D did predict the persistence of existing pain.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗