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M Pepi

Publications and source records attributed to M Pepi.

At least 37 records · Page 2Linked to original sources
PubMed1999

Adhesion of acinetobacter venetianus to diesel fuel droplets studied with In situ electrochemical and molecular probes

The adhesion of a recently described species, Acinetobacter venetianus VE-C3 (F. Di Cello, M. Pepi, F. Baldi, and R. Fani, Res. Microbiol. 148:237-249, 1997), to diesel fuel (a mixture of C12 to C28 n-alkanes) and n-hexadecane was studied and compared to that of Acinetobacter sp. strain RAG-1, which is known to excrete the emulsifying lipopolysaccharide, emulsan. Oxygen consumption rates, biomass, cell hydrophobicity, electrophoretic mobility, and zeta potential were measured for the two strains. The dropping-mercury electrode (DME) was used as an in situ adhesion sensor. In seawater, RAG-1 was hydrophobic, with an electrophoretic mobility (&mgr;) of -0.38 x 10(-8) m2 V-1 s-1 and zeta potential (zeta) of -4.9 mV, while VE-C3 was hydrophilic, with &mgr; of -0.81 x 10(-8) m2 V-1 s-1 and zeta of -10.5 mV. The microbial adhesion to hydrocarbon (MATH) test showed that RAG-1 was always hydrophobic whereas the hydrophilic VE-C3 strain became hydrophobic only after exposure to n-alkanes. Adhesion of VE-C3 cells to diesel fuel was partly due to the production of capsular polysaccharides (CPS), which were stained with the lectin concanavalin A (ConA) conjugated to fluorescein isothiocyanate and observed in situ by confocal microscopy. The emulsan from RAG-1, which was negative to ConA, was stained with Nile Red fluorochrome instead. Confocal microscope observations at different times showed that VE-C3 underwent two types of adhesion: (i) cell-to-cell interactions, preceding the cell adhesion to the n-alkane, and (ii) incorporation of nanodroplets of n-alkane into the hydrophilic CPS to form a more hydrophobic polysaccharide-n-alkane matrix surrounding the cell wall. The incorporation of n-alkanes as nanodroplets into the CPS of VE-C3 cells might ensure the partitioning of the bulk apolar phase between the aqueous medium and the outer cell membrane and thus sustain a continuous growth rate over a prolonged period.

Journal Article↗
PubMed1999

Lack of prognostic value of 99mTc MIBI rest, 18F FDG and 201TL rest/redistribution on PTCA outcome of patients with moderate left ventricle dysfunction.

BACKGROUND: The clinical work-out of patients undergoing coronary revascularization includes the assessment of myocardial viability. This approach has to be defined in the different classes of patients. The aim of this study was to evaluate the predictive prognostic value of different techniques on outcome following PTCA in patients with moderate left ventricle dysfunction (left ventricle EF > or = 40%). METHODS: Seventeen patients with EF > or = 40% and undergoing PTCA were studied by 201Tl rest/redistribution, 18F-FDG and 99mTc-MIBI rest. Regional kinesis was scored by echo, dividing left ventricle in 11 segments. The echo evaluation was repeated at 1 and 6 months after revascularization. RESULTS: Global EF was 52.5 +/- 7% and 69 segments had abnormal kinesis. Patients underwent stress/rest 99mTc-MIBI SPET, rest/redistribution 201Tl SPET and rest 18F-FDG PET. Among the 11 segments defined on echo-matched tomographic images, the one with the highest activity at stress was assumed as reference (activity = 100%). If > 50% of reference segment, 18F-FDG and 201Tl uptakes were considered significant. After PTCA, the echo-follow-up did not demonstrated significant improvement of left ventricle function at 30 days after PTCA (EF 56 +/- 6%) as well as at 6 months (EF 56 +/- 9%). The positive predictive value under these conditions resulted: 46.5% with 99mTc-MIBI rest, 47.4% with 201Tl rest-redistribution and 45.7% with 18F-FDG. CONCLUSIONS: In summary, in the class of patients with moderately compromised function, considering as reference the improved regional kinesis after PTCA, 99mTc-MIBI at rest, 201Tl rest/redistribution and 18F-FDG do not exhibit a clear predictive value; patient population is then a highly relevant point to establish the accuracy of these diagnostic procedures.

Adult↗
PubMed1998

Effect of sample volume location on Doppler-derived transmitral inflow velocity values in 288 normal subjects 20 to 80 years old: an echocardiographic, two-dimensional color Doppler cooperative study.

The aims of the study were to evaluate in a population of 288 normal subjects 20 to 80 years old (1) the normal values of the indexes of the mitral flow velocity pattern measured either at the tips of the mitral leaflets or at the annulus; (2) whether there was a significant difference between the values obtained at the tips compared with those measured at the mitral annulus; (3) the correlation with aging between the indexes measured in the two different positions; and (4) whether certain physiological variables have different effects on diastolic function measured in the two different positions. The highest values were always measured at the tips of the mitral leaflets (p < 0.05); only atrial filling fraction, E acceleration time, and E deceleration velocity had higher values when measured at the level of the annulus (p < 0.05). The A-wave peak velocity had the same mean value when measured at both the tips and at the annulus. A significant difference in the correlation between parameters measured at the tips of the mitral leaflets with age and at the annulus (with age) was observed for the following parameters: (1) peak E velocity, E integral, total integral and E acceleration showed better correlation with age when measured at the annulus (p < 0.02); (2) peak A velocity and A integral showed better correlation with age when measured at the tips of the mitral leaflets (p < 0.001). Multivariate analysis showed that age was the variable that had the most influence on diastolic function parameters; heart rate had less influence on the diastolic function indexes.

Adult↗
PubMed1997

Relation between exercise-induced left ventricular wall motion abnormalities and coronary artery disease in hypertensive patients: effects of blood pressure normalization.

In hypertension, several factors disturb coronary circulation and the metabolic reserve of the heart. This study was undertaken to test whether in hypertensive patients global and regional left ventricular (LV) function is related during exercise to the presence of significant coronary stenosis and whether lowering of coronary perfusion pressure through rapid normalization of the diastolic pressure may modify the dynamics of the left ventricle. Thirty-five patients with mild to moderate hypertension undergoing coronary angiography for the evaluation of chest pain were included in the study; upright bicycle exercise echocardiography tests were performed without therapy and 1 day later 1 h after sublingual administration of nifedipine. LV ejection fraction and regional wall motion scores were evaluated and compared at baseline, peak exercise, immediate postexercise, and recovery phases in each test through digital on-line storing of echocardiographic images. Twenty-one patients had normal coronary arteries (group 1) and 14 significant coronary stenoses (group 2); age, gender, heart rate, blood pressure, left ventricular diameter and mass index, and ejection fraction were similar in the two groups. At peak exercise LV ejection fraction slightly increased in group 1, whereas it slightly decreased in group 2 (both during the test without therapy and after nifedipine administration). All patients in group 1 had normal left ventricular wall motion during exercise; 13 of 14 patients in group 2 had LV wall motion abnormalities at peak exercise. Nifedipine did not produce any effect on LV regional wall motion in group 1, but it induced significant changes in LV regional wall motion in seven patients in group 2. Changes in LV wall motion between the two test groups were related to the number of the stenotic coronary vessels: the normal exercise test before and after therapy and the two normalized tests after nifedipine administration were in fact observed in patients with one-vessel disease, whereas worsening or changes in the site of ischemia were observed only in patients with multivessel disease. Regional and global left ventricular dynamics during exercise is mainly dependent on the existence of significant coronary artery disease. Rapid decrease of blood pressure does not alter the regional dynamics of the left ventricle during exercise in patients without coronary artery disease, but it may induce normalization, worsening, or changes in the site of wall motion abnormalities in hypertensives with significant coronary stenoses.

Aged↗
PubMed1997

Reduction of vanadate to vanadyl by a strain of Saccharomyces cerevisiae.

Three strains of Saccharomyces cerevisiae, SC-1, DBVPG 6173 and DBVPG 6037, were studied for vanadate resistance in complex Sabouraud medium since they did not thrive in different minimal media (yeast nitrogen base with and without amino acids). The strain SC-1 was resistant up to 16 mM of vanadate, whereas the strains DBVPG 6173 and DBVPG 6037 were inhibited by 8 mM and 4 mM vanadate, respectively. The vanadate resistance in strain SC-1 was constitutive and due to the reduction of this oxyanion to vanadyl, which was detected by EPR spectroscopy and visible spectroscopy. The transformation of vanadate to vanadyl took place during the exponential growth phase; 10 mM of vanadate was reduced to vanadyl outside the cells since the oxyanion was not detected in the cell biomass and only a negligible concentration of vanadyl (25 nmoles mg-1 cells dry weight) was found in the biomass. The other two vanadate-sensitive yeast strains only accumulated vanadate and did not reduce the oxyanion to vanadyl.

Biomass↗
PubMed1997

Tolerance to mercury chloride in Scenedesmus strains.

Mercury chloride toxicity was investigated in two strains of Chlorella and in a strain of Scenedesmus isolated from polluted areas in Tuscany (Italy). No Hg resistance was found in the autotrophic microorganisms isolated, but Scenedesmus sp. strain AR-2489, isolated from the Arno river, was able to grow at concentrations of up to 5 micrograms ml-1 of Hg. This concentration was twice that which inhibited growth of the two Chlorella strains and Scenedesmus acutus 8M, the reference strain from a culture collection. Photosynthesizing cells of Scenedesmus sp. AR-2489 showed reduced Hg uptake, with the highest percentage of Hg removal from the medium. Loss of Hg was not due to Hg(0) volatilization, as shown by a comparison test with the broad-spectrum Hg-resistant Pseudomonas putida FB1. The metabolic differences between Scenedesmus sp. strain AR-2489 and Siacatus strain 8M were: (1) higher growth rate (doubling time of 6.0 h versus 10.6 h); (2) higher O2 production rate (maximum 2 mumol h-1 mg-1 dry weight); and (3) higher intracellular pH during growth. The latter was imaged with a green fluorescence molecular probe (BCEFC-AM) and observed by scanning confocal laser microscopy (SCLM). The distribution of red-autofluorescence chlorophyll-a showed that strain AR-2489 had a rougher and hence more extended specific chloroplast surface than strain 8M. Hg tolerance in strain AR-2489 was related to the rapid increase in dissolved O2 in the medium and in intracellular pH; this caused a loss of soluble mercury transformed to insoluble mercury hydroxide, which is thermodynamically more stable at alkaline pH in highly oxygenated systems.

Chlorella↗
PubMed1997

Pulmonary venous flow velocity patterns in 143 normal subjects aged 20 to 80 years old. An echo 2D colour Doppler cooperative study.

In order to find out the normal values and to evaluate the effects of age, heart rate, sex, and haemodynamic and standard echocardiographic parameters on pulmonary venous flow velocity obtained by the transthoracic approach. Doppler pulmonary venous flow parameters were measured in 143 healthy subjects aged from 20 to 80 years. Doppler pulmonary venous flow parameters which had the best correlation with age were: the peak velocity of the systolic wave (r = 0.39) and its integral (r = 0.5), the peak velocity of the diastolic wave (r = -0.6) and its integral (r = -0.44); the systolic (r = 0.68) and diastolic fractions (r = -0.68); the systolic/diastolic peak velocity ratio (r = 0.73) and the systolic/diastolic integral ratio (r = 0.7). The atrial reversal wave did not correlate with age; the atrial reversal wave was more difficult and probably less reliable to measure than the systolic and diastolic waves. The correlations of pulmonary venous flow parameters with mitral flow parameters were also examined. This study showed that, in healthy subjects, despite an increase in the early and atrial waves from the annulus to the tips of the mitral leaflets, there is a similar association between pulmonary venous flow and mitral flow measured at the annulus or at the tips of the mitral leaflets. The intra-observer reproducibility of all the pulmonary venous flow parameters considered were found to be excellent. Moderate inter-observer variability was observed for the systolic, diastolic and atrial reversal wave peak velocities and integrals; however, the systolic/diastolic ratio improved the precision of the measurements. Multivariate analysis showed that age is the principal determinant of the Doppler parameters of pulmonary venous flow: heart rate, sex, body surface area, the size of the left atrium in systole and the left ventricular ejection fraction all influence the Doppler parameters of pulmonary venous flow, even if only slightly.

Adult↗
PubMed1997

["Diastology"].

Explore the source record for details and available documents.

Diastole↗
PubMed1996

Degradation of 3-nitrophenol by Pseudomonas putida B2 occurs via 1,2,4-benzenetriol.

Growth of Pseudomonas putida B2 in chemostat cultures on a mixture of 3-nitrophenol and glucose induced 3-nitrophenol and 1,2,4-benzenetriol-dependent oxygen uptake activities. Anaerobic incubations of cell suspensions with 3-nitrophenol resulted in complete conversions of the substrate to ammonia and 1,2,4-benzenetriol. This indicates that P. putida B2 degrades 3-nitrophenol via 1,2,4-benzenetriol, via a pathway involving a hydroxylaminolyase. Involvement of this pathway in nitroaromatic metabolism has previously only been found for degradation of 4-nitrobenzoate. Reduction of 3 nitrophenol by cell-free extracts was strictly NADPH-dependent. Attempts to purify the enzymes responsible for 3-nitrophenol metabolism were unsuccessful, because their activities were extremely unstable. 3-Nitrophenol reductase was therefore characterized in cell-free extracts. The enzyme had a sharp pH optimum at pH 7 and a temperature optimum at 25 degrees C. At 30 degrees C, reductase activity was completely destroyed within one hour, while at 0 degrees C, the activity in cell-free extracts was over 100-fold more stable. The Km values for NADPH and 3-nitrophenol were estimated at 0.17 mM and below 2 microM, respectively. The substrate specificity of the reductase activity was very broad: all 17 nitroaromatics tested were reduced by cell-free extracts. However, neither intact cells nor cell-free extracts could convert a set of synthesized hydroxylaminoaromatic compounds to the corresponding catechols and ammonia. Apparently, the hydroxylaminolyase of P. putida B2 has a very narrow substrate specificity, indicating that this organism is not a suitable biocatalyst for the industrial production of catechols from nitroaromatics.

Biodegradation, Environmental↗
PubMed1996

Dissolution of Barium from Barite in Sewage Sludges and Cultures of Desulfovibrio desulfuricans.

High concentrations of total barium, ranging from 0.42 to 1.58 mg(middot)g(sup-1) (dry weight) were found in sludges of two sewage treatment plants near Florence, Italy. Barium concentrations in the suspended matter decreased as redox potential values changed from negative to positive. An anoxic sewage sludge sample was aerated, and 30% of the total barium was removed in 24 h. To demonstrate that barium was solubilized from barite by sulfate-reducing bacteria, a strain of Desulfovibrio desulfuricans was used to study the solubilization of barium from barite under laboratory conditions. During cell growth with different concentrations of barite from 0.01 to 0.3 g(middot)liter(sup-1) (the latter is the MIC) as the only source of sulfates in the cultures, the D. desulfuricans strain accumulated barium up to 0.58 (mu)g(middot)mg(sup-1) (dry weight). Three times the quantity of barium was dissolved by bacteria than in the uninoculated medium (control). The unexpectedly low concentration of soluble barium (1.2 mg of Ba(middot)liter(sup-1)) with respect to the quantity expected (109 mg of Ba(middot)liter(sup-1)), calculated on the basis of the free H(inf2)S evolved from the dissimilatory reduction of sulfate from barite, was probably due to the formation of other barium compounds, such as witherite (BaCO(inf3)) and the transient species barium sulfide (BaS). The D. desulfuricans strain, growing on barite, formed visible aggregates. Confocal microscopy analysis showed that aggregates consisted of bacteria and barite. After 3 days of incubation, several autofluorescent crystals surrounded by a dissolution halo were observed. The crystals were identified as BaS by comparison with the commercial compound.

Journal Article↗
PubMed1996

Intraoperative multiplane vs biplane transesophageal echocardiography for the assessment of cardiac surgery.

This study was undertaken to test whether multiplane transesophageal echocardiography (TEE) offers advantages in comparison with biplane TEE in the intraoperative monitoring during cardiac surgery. A diagnostic multiplane TEE was performed in 400 patients in the immediate preoperative and postoperative periods. We systematically acquired cardiac images from the gastric fundus, lower esophagus, and upper esophagus; complete views of the descending aorta were also recorded. Usefulness of the different views in providing essential additional clinical information compared with exclusive transverse (0 to 20 degrees) and longitudinal (70 to 110 degrees) planes of the biplane TTE was assessed assuming that with manipulation of a biplane probe, a 20 degrees are could be added to the conventional horizontal and vertical planes. A high success rate of each view was demonstrated; anatomy and pathologic condition were best visualized in oblique planes. The method proved to be particularly useful in the preoperative and postoperative phases of aortic dissection (27 cases), aortic (65 cases) and mitral (35 cases) valve replacement, mitral valve repair (38 cases), left ventricular aneurysmectomy (25 cases), bleeding from proximal suture of an aortic heterograft (2 cases), and positioning of left ventricular hemopump (2 cases). Additional regional wall motion abnormalities of the right (four cases) and left ventricle (six cases) not appreciated in 0 to 20 degrees or 70 to 110 degrees planes were detected. Multiplane TEE is a useful clinical tool during intraoperative monitoring of cardiac surgery. Most structures of the heart and great vessels lie on oblique planes, while other views are optimized with the aid of slight angle corrections. This method improves the evaluation of anatomy and pathologic condition of the heart and great vessels, of native and prosthetic valves, and of left and right ventricular function.

Adolescent↗
PubMed1995

Lung-heart interaction as a substrate for the improvement in exercise capacity after body fluid volume depletion in moderate congestive heart failure.

We investigated exercise capacity after fluid depletion in patients with moderate congestive heart failure (CHF). Twenty-one patients underwent ultrafiltration (mean volume +/- SEM: 1,770 +/- 135 ml). Echocardiography, tests of pulmonary function, and a cardiopulmonary exercise test with hemodynamic and esophageal pressure monitoring were performed before ultrafiltration and 3 months later. Tests without invasive measurements were repeated 4 and 30 days after ultrafiltration. Twenty-one control patients followed the same protocol but did not have ultrafiltration. Patients who underwent ultrafiltration and increased their oxygen consumption at peak exercise (peak VO2) by > 10% at the 3-month evaluation (group A1, n = 9) were separated from those who did not (group A2, n = 8); 3 patients did not complete the follow-up. Four days after the procedure, peak VO2 had risen from 17.3 +/- 0.8 to 19.3 +/- 0.9 ml/min/kg in group A1, and from 11.9 +/- 0.7 to 14.1 +/- 0.7 ml/min/kg in group A2 (p < 0.01). Plasma norepinephrine and pulmonary function were consistent with a greater severity of the syndrome in group A2. At 3 months in group A1, the relations of filling pressure to cardiac index of the right and left ventricles were shifted upward; the esophageal pressure swing (differences between end-expiratory and end-inspiratory pressure) for a given tidal volume was lower; the peak exercise dynamic lung compliance had increased from 0.10 +/- 0.05 to 0.14 +/- 0.03 L/mm Hg (p < 0.01). None of these changes were detected in group A2 and control patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1995

Spatial registration of echocardiographic and positron emission tomographic heart studies.

A method has been developed to match corresponding heart regions from functional echocardiographic (Echo) and metabolic fluorine-18-fluoro-2-deoxy-D-glucose ([18F]FDG) positron emission tomography (PET) studies in individual patients. Echo and PET images are spatially correlated by determining homologous anatomical landmarks (the two papillary muscles and the inferior junction of the right ventricle), identifiable in images obtained by both acquisition modalities. Echo-PET image registration is first performed in the plane identified by the three landmarks, using a rigid rotate-translate scale model. The registration parameters are then used to transform the whole PET volume. This allows a consistent Echo-PET regional analysis, according to a segmental subdivision of the heart. The technique was tested on patients. The overlay of Echo and PET registered images proved the reliability of realignment of the three markers and a good spatial correlation of myocardial walls. This approach to image registration could be applied to other acquisition modalities (such as magnetic resonance imaging and single-photon emission tomography), provided that the three anatomical landmarks are visualized.

Deoxyglucose↗