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Biomedical subjects

G Riccardi

Publications and source records attributed to G Riccardi.

At least 73 records · Page 4Linked to original sources
PubMed1998

Functional food science and substrate metabolism.

The present review addresses the role of food constituents in the aetiology of metabolic conditions and chronic diseases, mostly related to energy metabolism and substrate regulation, such as obesity and non-insulin-dependent diabetes mellitus. Second, attention is paid to malnutrition, a major cause of mortality and morbidity in developing countries, which may be a cause of concern in Europe because of the increasing number of elderly people in the population. Finally, the role of diet during exercise, a condition of enormous substrate demands, is evaluated. Based on a critical evaluation of the existing knowledge in the literature, implications for future research in relation to functional foods are discussed.

Adolescent↗
PubMed1998

Molecular cloning and functional analysis of a novel tetracycline resistance determinant, tet(V), from Mycobacterium smegmatis.

The nucleotide sequence and mechanism of action of a tetracycline resistance gene from Mycobacterium smegmatis were determined. Analysis of a 2.2-kb sequence fragment showed the presence of one open reading frame, designated tet(V), encoding a 419-amino-acid protein (molecular weight, 44,610) with at least 10 transmembrane domains. A database search showed that the gene is homologous to membrane-associated antibiotic efflux pump proteins but not to any known tetracycline efflux pumps. The steady-state accumulation level of tetracycline by M. smegmatis harboring a plasmid carrying the tet(V) gene was about fourfold lower than that of the parental strain. Furthermore, the energy uncoupler carbonyl cyanide m-chlorophenylhydrazone blocked tetracycline efflux in deenergized cells. These results suggest that the tet(V) gene codes for a drug antiporter which uses the proton motive force for the active efflux of tetracycline. By primer-specific amplification the gene appears to be restricted to M. smegmatis and M. fortuitum.

Amino Acid Sequence↗
PubMed1998

The MTCY428.08 gene of Mycobacterium tuberculosis codes for NAD+ synthetase.

The product of the MTCY428.08 gene of Mycobacterium tuberculosis shows sequence homology with several NAD+ synthetases. The MTCY428.08 gene was cloned into the expression vectors pGEX-4T-1 and pET-15b. Expression in Escherichia coli led to overproduction of glutathione S-transferase fused and His6-tagged gene products, which were enzymatically assayed for NAD synthetase activity. Our results demonstrate that the MTCY428.08 gene of M. tuberculosis is the structural gene for NAD+ synthetase.

Amino Acid Sequence↗
PubMed1998

mmr, a Mycobacterium tuberculosis gene conferring resistance to small cationic dyes and inhibitors.

The mmr gene, cloned from Mycobacterium tuberculosis, was shown to confer to Mycobacterium smegmatis resistance to tetraphenylphosphonium (TPP), erythromycin, ethidium bromide, acriflavine, safranin O, and pyronin Y. The gene appears to code for a protein containing four transmembrane domains. Studies of [3H]TPP intracellular accumulation strongly suggest that the resistance mediated by the Mmr protein involves active extrusion of TPP.

Amino Acid Sequence↗
PubMed1998

Plasma fibrinogen: a new factor of the metabolic syndrome. A population-based study.

OBJECTIVE: To evaluate whether hyperfibrinogenemia represents a component of the metabolic syndrome. RESEARCH DESIGN AND METHODS: A cross-sectional study was conducted on the relation between fibrinogen and the metabolic syndrome in a working population of 1,252 nondiabetic men, aged 35-64 years, randomly selected among all men participating in a health screening. We measured anthropometric characteristics, blood pressure, fasting plasma fibrinogen, cholesterol (total, LDL, and HDL), triglycerides, glucose, and insulin. Individuals with two or more metabolic abnormalities (defined as being in the highest quartile of the distribution of diastolic blood pressure, plasma glucose, or triglycerides or being in the lowest quartile of HDL cholesterol) were considered to have the metabolic syndrome. RESULTS: Age-adjusted fibrinogen levels correlated significantly with BMI, waist-to-hip ratio, systolic and diastolic blood pressure, plasma total cholesterol, LDL cholesterol, triglycerides, insulin, and HDL cholesterol (inversely). Subjects with the metabolic syndrome had significantly higher plasma fibrinogen levels than those without (285.1 +/- 1.9 vs. 300.2 +/- 3.0 mg/dl, mean +/- SE, P = 0.0001). Plasma fibrinogen concentrations and the prevalence of hyperfibrinogenemia (defined as > or = 350 mg/dl) increased progressively from 279 to 307 mg/dl (P = 0.0001) and from 9 to 22% (P = 0.0024), respectively, across categories with an increasing number of metabolic disorders characterizing the syndrome (only one, any two, three or more). In multivariate analyses, both plasma insulin and the metabolic syndrome were significantly and independently associated with plasma fibrinogen. CONCLUSIONS: The finding suggests that hyperfibrinogenemia may be considered a component of the metabolic syndrome. This may also explain the increased cardiovascular risk associated with hyperinsulinemia/insulin resistance.

Adult↗
PubMed1997

In skeletal muscle, glucose storage and oxidation are differentially impaired by the IR1152 mutant receptor.

L6 myotubes expressing the constitutively active Arg1152-->Gln insulin receptor (L6(1152)) featured a 31% increased glucose consumption as compared with L6 cells expressing wild-type receptors (L6(WT)). However, insulin treatment decreased glucose consumption of the mutant cells by 20% while increasing that of the L6(WT) by 30%. In the L6(WT), insulin elicited a significant increase in glucose transport and GLUT1 and GLUT4 plasma membrane expression, while in the L6(1152), all of these functions were constitutively activated and not further stimulated by insulin. Similarly, glycogen content and glycogen synthase activity were increased by 80 and 125%, respectively, in the L6(1152 )versus the L6(WT) and unaffected by insulin (while a 2-fold increase was measured in insulin-exposed L6(WT)). Glucose oxidation and pyruvate dehydrogenase activity were also 25% higher in the mutant compared with the L6(WT). However, in the L6(1152), both functions decreased by 35% in response to insulin (while increasing by 60 and 80%, respectively, in the L6(WT)). Similarly as in the L6(1152), in vivo, forearm glucose uptake in IR1152 patients was 2-fold higher than in control subjects. This difference was not accounted for by higher plasma glucose levels. We conclude that, in skeletal muscle, glucose storage and oxidation are differentially impaired by the expression of IR1152, suggesting that their regulation by insulin involves divergent signaling pathways. Muscle expression of IR1152 may contribute to impairing glucose tolerance in IR1152 individuals.

Cell Line↗
PubMed1997

Abnormal glucose transport and GLUT1 cell-surface content in fibroblasts and skeletal muscle from NIDDM and obese subjects.

Glucose transport and GLUT1 expression were studied in fibroblasts from 7 lean and 5 obese non-insulin-dependent diabetic (NIDDM) subjects with at least 2 NIDDM first-degree relatives and from 12 lean and 5 obese non-diabetic subjects with no family history of diabetes. The obese individuals also had a strong family history of obesity. Fibroblasts from all of the subjects exhibited no difference in insulin receptor binding, autophosphorylation, and kinase and hexokinase activity. At variance, basal 2-deoxyglucose (2-DG) uptake and 3H-cytochalasin B binding were 50% increased in cells from individuals with NIDDM (p < 0.001) and/or obesity (p < 0.01) as compared to the lean non-diabetic subjects. Insulin-dependent (maximally stimulated-basal) 2-DG uptake and cytochalasin B binding were decreased three-fold in cells from the diabetic and/or obese subjects (p < 0.01). GLUT1 mRNA and total protein levels were comparable in fibroblasts from all the groups. However, basal GLUT1 cell-surface content was 50% greater in fibroblasts from the NIDDM and/or obese subjects as compared to the lean non-diabetic individuals while insulin-dependent GLUT1 recruitment at the cell surface was diminished three-fold. Increased basal GLUT1 content in the plasma membrane was also observed in skeletal muscle of 4 NIDDM and 3 non-diabetic obese individuals (p < 0.05 vs the lean non diabetic subjects). Basal 2-DG uptake in fibroblasts from diabetic/obese individuals and lean control subjects strongly correlated with the in vivo fasting plasma insulin concentration of the donor. A negative correlation was demonstrated between the magnitude of insulin-dependent glucose uptake by the fibroblasts and plasma insulin levels in vivo. We conclude that a primary abnormality in glucose transport and GLUT1 cell-surface content is present in fibroblasts from NIDDM and obese individuals. The abnormal GLUT1 content is also present in skeletal muscle plasma membranes from NIDDM and obese individuals.

Adult↗
PubMed1997

Dobutamine and nitroprusside infusion in patients with severe congestive heart failure: hemodynamic improvement by discordant effects on mitral regurgitation, left atrial function, and ventricular function.

OBJECTIVES: In patients with severe heart failure additional therapeutic support with intravenous inotropic or vasodilator drugs is frequently used in the attempt to obtain hemodynamic control. The nature and extent to which diastolic filling, atrial function, and mitral regurgitation are modified by these drugs have not been fully explored. The aim of this study was to compare the acute adaptations of the left ventricular performance, left atrial function, and mitral regurgitation that accompanied hemodynamic improvement during intravenous dobutamine and nitroprusside infusions in patients with severe chronic heart failure. METHODS: Forty consecutive patients with severe heart failure were evaluated by simultaneous echo-Doppler and hemodynamic investigations at baseline and during nitroprusside and dobutamine administration. Mitral flow velocity variables, left atrial and ventricular volumes, left atrial reservoir, conduit and pump volumes, and mitral regurgitation jet area were compared by analysis of variance for repeated measurements. RESULTS: Nitroprusside increased cardiac output (2.1 +/- .5 vs 2.6 +/- .5 L/min/m2, p < 0.004), reduced left ventricular filling pressure (25 +/- 6 vs 14 +/- 4 mm Hg, p < 0.0001), and improved left atrial pump volume (19 +/- 3 vs 26 +/- 12 ml, p < 0.02) without variations in left atrial reservoir and conduit volume. The restoration of preload reserve and improvement of the atrial contribution to left ventricular diastolic filling were demonstrated by the Doppler mitral flow pattern, which moved from a restrictive to a normal pattern. Furthermore mitral regurgitation decreased in all patients (9 +/- 4.6 vs 4.6 +/- 3.4 cm2, p < 0.0001). Dobutamine increased cardiac output (2.1 +/- .5 vs 2.8 +/- .6 L/min/m2), but the effects on pulmonary wedge pressure and mitral regurgitation were variable and unpredictable. Left atrial reservoir and conduit volumes increased, whereas left atrial pump volume did not change (19 +/- 13 vs 22 +/- 14 ml, p = NS). Furthermore Doppler mitral flow showed a persistent restrictive pattern. CONCLUSIONS: In patients with advanced congestive heart failure both nitroprusside and dobutamine improve cardiac output, with different adaptations of left ventricular performance and left atrial function. Nitroprusside seems to restore both atrial and ventricular pump function better. Careful echo-Doppler monitoring during drug infusion provides information relevant to the clinical treatment of individual patients.

Atrial Function, Left↗
PubMed1997

Factors related to glycemic control in IDDM and insulin-treated NIDDM patients in current practice. A comparison of care policies. SIEMTIC Group. Studio Italiano Epidemiologico Multicentrico su Terapia Insulin e Controllo Metabolico.

OBJECTIVE: To evaluate, under routine conditions, the relation between different diabetes care policies and glycemic control through a by-center analysis procedure aimed at reducing some drawbacks of cross-sectional data. RESEARCH DESIGN AND METHODS: A survey on insulin-treated diabetes care management (IDDM and NIDDM) involved 16 Italian randomly selected diabetes outpatient clinics. A total of 2,142 representative patients were investigated. The standardized HbA1c average value of each center was related, by regression models, to some indicators of center care policy (average number of injections, average BMI, proportion of cases with recent fundus oculi examinations, or frequent visits) as well as to patients' average social levels (employment type). Homogeneity in patient admission criteria is assumed among the investigated centers as a basic condition for the procedure validity. Some known imbalance were controlled for both design and analysis. RESULTS: HbA1c showed a univariate inverse relation with daily number of injections in IDDM (P = 0.0009, r2 = 0.56) but not in NIDDM (P = 0.33). It was inversely related to both fundus examination (IDDM P = 0.04; NIDDM P = 0.099) and qualified employment (IDDM P = 0.06; NIDDM P = 0.026). A stepwise regression analysis left in the model insulin injections (P = 0.0002) in IDDM (total r2 = 0.68) and qualified employment (P = 0.016) and fundus examination (P = 0.14) in NIDDM (total r2 = 0.53), after controlling for age, sex, disease duration, insulin therapy starting delay, and insulin dose per kilogram. CONCLUSIONS: These results suggest that the confirmed benefits of a multiple-injection regimen in IDDM cannot be simply extrapolated to NIDDM, where patients' awareness and medical attention to complications proved to be the most important factors in current practice.

Adult↗
PubMed1997

Insulin and sulfonylurea therapy in NIDDM patients. Are the effects on lipoprotein metabolism different even with similar blood glucose control?

This study evaluates the effects of insulin versus glibenclamide on lipoprotein metabolism at comparable levels of blood glucose control, in particular on the concentration and distribution of VLDL subfractions and lipolytic enzyme activities in nine NIDDM men (aged 56 +/- 3 years, BMI 26.5 +/- 0.9 kg/m2) (means +/- SE) participating in a crossover study. After a 3-week washout period, patients were randomly assigned to 2-month treatment periods (insulin or glibenclamide); thereafter, each patient crossed to the other treatment. At the end of each period, mean daily blood glucose (MDBG), HbA1e, plasma lipids, lipoproteins (VLDL, LDL, HDL), lipoprotein subfractions (VLDL1, 2, 3; HDL2, HDL3), and post-heparin lipase activities (lipoprotein lipase [LPL], hepatic lipase [HL]) were evaluated. Although glucose control was similar at the end of both periods (MDBG 8.3 +/- 0.3 vs. 7.9 +/- 0.3 mmol/l; HbA1c 7.4 +/- 0.3 vs. 7.0 +/- 0.2%, insulin versus glibenclamide), insulin compared with glibenclamide induced a significant reduction in plasma triglycerides (0.9 +/- 0.1 vs. 1.1 +/- 0.1 mmol/l, P < 0.05), VLDL triglycerides (50.1 +/- 12.2 vs. 63.6 +/- 12.3 mg/dl, P < 0.02), VLDL1 lipid concentration (24.9 +/- 7.5 vs. 39.9 +/- 9.5 mg/dl, P < 0.006), and increased HDL2 cholesterol (25.2 +/- 1.6 vs. 20.3 +/- 1.3 mg/dl, P < 0.03). In terms of VLDL percentage subfraction distribution, with insulin, there was a decrease in the larger subfractions (VLDL1 26.5 +/- 3.0 vs. 37.8 +/- 3.4%, P < 0.02) and an increase in the smallest (VLDL3 47.3 +/- 3.8 vs. 37.3 +/- 3.3%, P < 0.05). Moreover, HL activity was significantly lower after insulin than after glibenclamide (HL 247.2 +/- 22.3 vs. 263.5 +/- 22.6 mU/ml, P < 0.05). In conclusion, compared with glibenclamide, insulin treatment (independent of variations in glucose control) is able to decrease significantly plasma triglycerides, to increase HDL2 cholesterol, and to reduce only the concentration of the larger VLDL subfractions, with a consequent redistribution of their profile.

Blood Glucose↗
PubMed1996

Cloning and sequencing of the ilvBNC gene cluster from Mycobacterium avium.

Disseminated Mycobacterium avium (Ma)-M. intracellulare disease is a prevalent opportunistic infection in patients with Acquired Immune Deficiency Syndrome. Mycobacteria produce a variety of fatty acids which provide the first line of defence against potentially lethal environmental conditions. The metabolism of the branched-chain amino acids (BCAA) could be correlated to the production of branched-chain fatty acids in mycobacteria. In order to develop a better understanding of Mycobacterium BCAA biosynthesis, three genes, ilvBN and ilvC, encoding acetohydroxy acid synthase (AHS) and acetohydroxy acid isomeroreductase (IR), respectively, were cloned from Ma. The genes were isolated by screening a Ma genomic library with a heterologous probe. The deduced amino acid sequences revealed significant homology to the AHS and IR proteins from other bacterial species.

Acetolactate Synthase↗
PubMed1996

Sequence of the Bacillus stearothermophilus gene encoding aspartokinase II.

The complete nucleotide sequence of the gene encoding aspartokinase (Ask) II from thermophilic Bacillus stearothermophilus has been determined. Degenerate oligodeoxyribonucleotides primed the amplification of a 932-bp gene. This sequence was successively used for constructing new primers applied in inverse polymerase chain reaction using, as template, self-ligating DNA fragments. The deduced amino-acid sequence is 68.7% identical with the sequence of the Bacillus sp. strain MGA3 Ask II.

Amino Acid Sequence↗
PubMed1996

Does impaired glucose tolerance predict hypertension? A prospective analysis.

This study evaluates prospectively the relationship between impaired glucose tolerance (IGT) and blood pressure. From a population of 1376 men and women aged 40-59 years, all those with IGT (n = 54) plus 133 age- weight- and sex-matched normoglycaemic control subjects were selected after excluding treated hypertensive patients. Blood pressure, fasting and postload blood glucose and plasma insulin were measured. At 11.5 years after the first visit 76% of the IGT patients and 80% of the control subjects were re-examined. At baseline blood pressure was significantly higher in IGT patients than in control subjects (systolic 135.5 +/- 2.3 vs 127.9 +/- 1.4 mmHg, p < 0.001; and diastolic 88.0 +/- 1.5 vs 84.7 +/- 0.7 mm Hg, p < 0.05) independent of age, gender, weight, antihypertensive medication and insulinaemia. Accordingly, hypertension was more frequent in subjects with IGT (odds ratio 2.1, 95% confidence, interval (CI) 0.9-4.9). Postload insulin was significantly associated with hypertension--both at univariate and multivariate analysis--in normoglycaemic subjects, but not in those with IGT. At follow-up systolic blood pressure increased in both groups; the increase was smaller in patients with IGT (6.0 +/- 2.4 vs 12.3 +/- 1.6 mm Hg p < 0.05). Likewise, the 11.5 years' cumulative incidence of hypertension was not significantly different in subjects with baseline IGT or normoglycaemia; if anything it was lower in the IGT group (odds ratio 0.36, 95% CI 0.1-1.2). In multivariate analysis incidence of hypertension was associated positively with baseline blood pressure (p < 0.0003) and negatively with IGT status p < 0.03), while no significant association was found with insulin. In conclusion, the findings of this study question IGT as a risk factor for hypertension. Furthermore, these data do not indicate a major role for hyperglycaemia and hyperinsulinaemia per se in the aetiology of hypertension and suggest that IGT and hypertension share one or more pathogenetic factor(s) (i.e., insulin resistance, hyperactivity of the sympathetic nervous system, etc.), which induce deterioration of blood pressure control first, and hyperglycaemia later.

Adult↗
PubMed1996

The katE gene, which encodes the catalase HPII of Mycobacterium avium.

Disseminated Mycobacterium avium-Mycobacterium intracellulare disease is a prevalent opportunistic infection in patients with acquired immune deficiency syndrome (AIDS). These pathogens are generally resistant to isoniazid (INH), a powerful antituberculosis drug. It is now generally accepted that the INH susceptibility of Mycobacterium tuberculosis results from the transformation of the drug into a toxic derivative, as a result of the action of the enzyme catalase-peroxidase (HPI), encoded by the katG gene. It has been speculated that the presence of a second catalase (HPII) in some mycobacterial species, but lacking in M. tuberculosis, may impair the action of INH. In this report, the nucleotide sequence of the M. avium katE gene, encoding catalase HPII, is described. This enzyme shows strong similarity to Escherichia coli catalase HPII and eukaryotic catalases. All amino acids previously postulated as participating directly in catalysis by liver catalase and most of the amino acids binding the prosthetic group are conserved in M. avium catalase HPII. The enzyme is expressed in E. coli and is inhibited by 3-amino-1,2,4-triazole (AT). Furthermore, Southern blot hybridizations and polymerase chain reaction experiments demonstrate the distribution of katE gene in several mycobacterial species. To evaluate the potentially antagonistic effect of HPII catalase on INH susceptibility, the katE gene was transformed into M. tuberculosis H37Rv and the minimum inhibitory concentration (MIC) for INH was determined. Despite strong expression of the katE gene, no change in MIC was observed, thus ruling out a possible contribution of this enzyme to the natural resistance of M. avium to the drug. The availability of the gene probe, encoding the second mycobacterial catalase HPII, should open the way for the development of new drugs and diagnostic tests to combat drug-resistant pathogen strains.

Amino Acid Sequence↗
PubMed1996

Gene arrangement and organization in a approximately 76 kb fragment encompassing the oriC region of the chromosome of Mycobacterium leprae.

A continuous 75627 bp segment of the Mycobacterium leprae chromosome spanning the oriC region was sequenced. The gene order at this locus was similar to that found in the replication origin region of many other prokaryotes, particularly Mycobacterium tuberculosis and Streptomyces coelicolor. As in the case of several Gram-positive bacteria, essential genes involved in basic cellular functions, such as DNA or RNA metabolism (dnaA, dnaB, dnaN, gyrB, gyrA, pcnB, recF, rnpA, ssb), cell wall synthesis (ponA, pbpA) and probably cell division (gidB, rodA) were found. Strikingly, the gidA gene was absent from this part of the genome and there was no rRNA operon near oriC. The gyrA gene harbours an intein coding sequence indicating that protein splicing is required to produce the mature A subunit of DNA gyrase. Among the many other noteworthy features were ORFs encoding putative serine/threonine protein kinases and a protein phosphatase, three tRNA genes, one M. leprae-specific repetitive element and a glnQ pseudogene.

Amino Acid Sequence↗
PubMed1996

Organization of the origins of replication of the chromosomes of Mycobacterium smegmatis, Mycobacterium leprae and Mycobacterium tuberculosis and isolation of a functional origin from M. smegmatis.

The genus Mycobacterium is composed of species with widely differing growth rates ranging from approximately three hours in Mycobacterium smegmatis to two weeks in Mycobacterium leprae. As DNA replication is coupled to cell duplication, it may be regulated by common mechanisms. The chromosomal regions surrounding the origins of DNA replication from M. smegmatis, M. tuberculosis, and M. leprae have been sequenced, and show very few differences. The gene order, rnpA-rpmH-dnaA-dnaN-recF-orf-gyrB-gyrA, is the same as in other Gram-positive organisms. Although the general organization in M. smegmatis is very similar to that of Streptomyces spp., a closely related genus, M. tuberculosis and M. leprae differ as they lack an open reading frame, between dnaN and recF, which is similar to the gnd gene of Escherichia coli. Within the three mycobacterial species, there is extensive sequence conservation in the intergenic regions flanking dnaA, but more variation from the consensus DnaA box sequence was seen than in other bacteria. By means of subcloning experiments, the putative chromosomal origin of replication of M. smegmatis, containing the dnaA-dnaN region, was shown to promote autonomous replication in M. smegmatis, unlike the corresponding regions from M. tuberculosis or M. leprae.

Bacterial Proteins↗