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Biomedical subjects

A Calzolari

Publications and source records attributed to A Calzolari.

At least 19 recordsLinked to original sources
PubMed2006

Effect of magnetic impurities in a two-band superconductor: a point-contact study of mn-substituted single crystals.

We present the first results of directional point-contact measurements in Mg1-xMnxB2 single crystals, with x up to 0.015 and bulk Tc down to 13.3 K. The order parameters Deltasigma and Deltapi were obtained by fitting the conductance curves with the two-band Blonder-Tinkham-Klapwijk model. BothDeltapi and Deltasigma decrease with the critical temperature of the junctions TAC, but remain clearly distinct up to the highest Mn content. Once analyzed within the Eliashberg theory, the results indicate that spin-flip scattering is dominant in the sigma band, as also confirmed by first-principles band-structure calculations.

Journal Article↗
PubMed2005

First-principles theory of correlated transport through nanojunctions.

We report the inclusion of electron-electron correlation in the calculation of transport properties within an ab initio scheme. A key step is the reformulation of Landauer's approach in terms of an effective transmittance for the interacting electron system. We apply this framework to analyze the effect of short-range interactions on Pt atomic wires and discuss the coherent and incoherent correction to the mean-field approach.

Journal Article↗
PubMed2003

Cardiovascular hemodynamics: relationships with insulin resistance in obese children.

We investigated blood pressure (BP), cardiac output (CO), and systemic vascular resistance (SVR) and their relationships with insulin and glucose blood levels in a group of 24 obese children (mean age, 11.9 +/- 2.1 years; 19 males). The data were compared to those obtained from a group of 19 healthy controls of the same age (12.4 +/- 2.1 years; p = NS; 13 males). BP at rest was measured and all subjects underwent an exercise testing on the treadmill (Bruce Prot.), time of exercise, maximal heart rate, maximum systolic blood pressure, CO, and SVR at rest and at peak exercise were considered. Only in the OC group were an oral glucose tolerance test were performed to calculate insulin sensitivity index (ISI) and echocardiography performed to determine the left ventricular mass (LVM). The relationships between cardiovascular and metabolic parameters were investigated. Student's t-test and linear regression analysis were used when appropriate. OC had a significant reduction in TE and higher BP, and linear regression analysis showed significant correlations between BP, ISI, and LVM. We speculate that OC need a regular cardiovascular and metabolic screening to prevent the development of early cardiovascular damage.

Cardiac Output↗
PubMed2003

Cardiopulmonary performances in young children and adolescents born with large abdominal wall defects.

BACKGROUND/PURPOSE: As long as the survival rate of patients with abdominal wall defects (AWD) increases, information about long-term follow-up is becoming necessary. Even though quality of life in these patients, in absence of associated anomalies, appears to be unaffected, respiratory impairment soon after birth has been documented; therefore, participation in sports rarely is addressed. METHODS: Eighteen patients, ranging in age from 7 to 18 years, operated on at birth for large abdominal wall defects (> 4 cm for gastroschisis; >6 cm for omphalocele) were asked to come for a stress test on a treadmill, with measurements of time of exercise (TE), maximal oxygen consumption (VO2 max) and continuous recording of vital parameters. Respiratory function also was assessed by Forced Vital Capacity (FVC). RESULTS: Ergometric data were compared with those of a normal pediatric population. All patients were able to perform the stress test with no cardiovascular abnormalities detected at rest or on exertion. Maximum heart rate was reached after a significantly shorter TE, and VO2 max was significantly reduced when comparing normal subjects with AWD subjects and AWD subjects in sports with those sedentary. FVC was only slightly reduced in AWD patients without reaching statistical significance. CONCLUSIONS: These findings indicate that patients operated on for AWD at birth exhibit a normal cardiorespiratory function; decreased TE and VO2 max are likely to reflect a lack of physical activity with a lower degree of fitness. Therefore, no limitations to motor performances should exist for these patients. Well-being may be greatly improved by regular exercise.

Adolescent↗
PubMed2002

Does chronic pacing affect exercise capacity after Mustard operation for transposition of the great arteries?

Late survival after Mustard repair of transposition of the great arteries is generally good but is often characterized by progressive deterioration of ventricular function and by late postsurgical arrhythmias, thus imposing the need for permanent pacing. To evaluate how chronic pacing affects long-term exercise capacity, we compared two groups of these patients: group 1, comprising 12 patients, aged 9.0 +/- 2.6 years, without pacemaker; and group 2, comprising 18 patients, aged 9.3 +/- 2.0 years, with pacemaker. Patient evaluation included history, physical examination electrocardiograph, Holter monitoring, and echocardiography. Pacing modes were as follows: AAI (6 patients), AAIR (9 patients), VVI (2 patients), and VVIR (1 patient). At exercise test we evaluated exercise tolerance, maximum heart rate, blood pressure, oxygen consumption, and cardiac output at rest and at peak exercise. The two groups were comparable for all variables examinated. All pacemakers showed normal function. During the exercise, 11 of 12 patients in group 1 showed sinus rhythm, and in group 2, 11 patients showed sinus rhythm, 5 junctional rhythm, and 2 continuous pacing. There were no significant differences between groups. Chronically paced Mustard patients but with restoration of spontaneous rhythm during the exercise test do not show reduced exercise tolerance in comparison with nonpaced Mustard patients.

Arrhythmias, Cardiac↗
PubMed2001

Exercise testing and 24-hour ambulatory blood pressure monitoring in children with Williams syndrome.

The aim of the study was to assess workload capacity and blood pressure (BP) response to treadmill exercise and 24-hour BP monitoring in children with Williams syndrome. Seventeen children were examined (8 males and 9 females) whose mean age was 13.8 +/- 3.6 years. Six patients were on antihypertensive therapy. Each patient underwent clinical examination and measurement of BP at rest, during exercise, and during 24-hour monitoring. Two-dimensional echocardiogram and echo-Doppler of renal arteries were performed. The test was stopped for muscular fatigue or reduced cooperation. The patients, when compared to a population of healthy children, had reduced total time of exercise (7.3 +/- 1.9 vs 14.3 +/- 2.6 min, p < 0.001) and, at the same workload, increased heart rate (167 +/- 19 vs 145 +/- 16 beats/min, p < 0.001) and increased maximum systolic BP (146 +/- 27 vs 128 +/- 12 mmHg, p = 0.01). Ambulatory blood pressure measurement values showed higher systolic blood pressure both during daytime and nighttime. Our study confirms that children and adolescents with Williams syndrome are at high risk for hypertension, probably related to the alterations of large arteries. The data relating to the synthesis of elastin may have a direct relationship to the compliance of the arterial system, leading to hypertension.

Adolescent↗
PubMed2001

Josephson effect in MgB(2) break junctions.

We present the first observation of the dc and ac Josephson effect in MgB(2) break junctions. The junctions, obtained at 4.2 K in high-quality, high-density polycrystalline metallic MgB(2) samples, show a nonhysteretic dc Josephson effect. By irradiating the junctions with microwaves we observe clear Shapiro steps spaced by the ideal Delta V value. The temperature dependence of the dc Josephson current and the dependence of the height of the steps on the microwave power are obtained. These results directly prove the existence of pairs with charge 2e in MgB(2) and give evidence of the superconductor-normal metal-superconductor weak link character of these junctions.

Journal Article↗
PubMed2001

Accentuated response to phenylhydrazine and erythropoietin in mice genetically impaired for their GATA-1 expression (GATA-1(low) mice).

The response of mice genetically unable to up-regulate GATA-1 expression (GATA-1(low) mice) to acute (phenylhydrazine [PHZ]-induced anemia) and chronic (in vivo treatment for 5 days with 10 U erythropoietin [EPO] per mouse) erythroid stimuli was investigated. Adult GATA-1(low) mice are profoundly thrombocytopenic (platelet counts [x 10(9)/L] 82.0 +/- 28.0 vs 840 +/- 170.0 of their control littermates, P <.001) but have a normal hematocrit (Hct) (approximately.47 proportion of 1.0 [47%]). The spleens of these mutants are 2.5-fold larger than normal and contain 5-fold more megakaryocytic (4A5(+)), erythroid (TER-119(+)), and bipotent (erythroid/megakaryocytic, TER-119(+)/4A5(+)) precursor cells. Both the marrow and the spleen of these animals contain higher frequencies of burst-forming units-erythroid (BFU-E)- and colony-forming units-erythroid (CFU-E)-derived colonies (2-fold and 6-fold, respectively) than their normal littermates. The GATA-1(low) mice recover 2 days faster from the PHZ-induced anemia than their normal littermates (P <.01). In response to EPO, the Hct of the GATA-1(low) mice raised to.68 proportion of 1.0 (68%) vs the.55 proportion of 1.0 (55%) reached by the controls (P <.01). Both the GATA-1(low) and the normal mice respond to PHZ and EPO with similar (2- to 3-fold) increases in size and cellularity of the spleen (increases are limited mostly to cells, both progenitor and precursor, of the erythroid lineage). However, in spite of the similar relative cellular increases, the increases of all these cell populations are significantly higher, in absolute cell numbers, in the mutant than in the wild-type mice. In conclusion, the GATA-1(low) mutation increases the magnitude of the response to erythroid stimuli as a consequence of the expansion of the erythroid progenitor cells in their spleen.

Anemia↗
PubMed2001

Cardiorespiratory functional assessment after pediatric heart transplantation.

Limited data are available on the exercise capacity of young heart transplant recipients. The aim of this study was therefore to assess cardiorespiratory responses to exercise in this group of patients. Fourteen consecutive heart transplant recipients (six girls and eight boys, age-range 5-15 yr) and 14 healthy matched controls underwent a Bruce treadmill test to determine: duration of test; resting and maximum heart rates; maximum systolic blood pressure; peak oxygen consumption (VO2 peak); and cardiac output. Duration of test and heart rate increase were then compared with: time since transplantation, rejections per year, and immunosuppressive drugs received. The recipients also underwent the following lung function tests: forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1). When compared with healthy controls, transplant recipients had tachycardia at rest (126 +/- 3.7 beats/min; p < 0.001); significantly reduced tolerance (9.3 +/- 0.4 min; p < 0.001), a maximum heart rate of 169 +/- 5.4 beats/min (p < 0.05); a cardiac output of 5.65 +/- 0.6 L/min (p < 0.05); and a lower heart-rate increase from rest to peak exercise (p < 0.001) but a similar VO2 peak. The heart-rate increase correlated significantly with time post-transplant (r = 0.55; p < 0.05), number of rejection episodes per year (r = - 0.63; p < 0.05), and number of immunosuppressive drugs (r = - 0.60; p < 0.05). The recipients had normal FVC and FEV1 values. After surgery, few heart transplant recipients undertake physical activity, possibly owing to over-protective parents and teachers and to a lack of suitable supervised facilities. The authors stress the importance of a cardiorespiratory functional evaluation for assessment of health status and to encourage recipients, if possible, to undertake regular physical activity.

Adolescent↗
PubMed2001

Exercise and sports participation after surgery for congenital heart disease: the European perspective.

The success of surgery for congenital heart disease which has been performed since many years has created a population of patients who require careful follow-up in order to determine their clinical progress and to establish the type and intensity of physical activity which they can safely perform. The authors illustrate the opinion of the European Community regarding children, sport and organizational aspects and also problems concerning the management of pediatric cardiac patients in Europe and Italy. Cardiological and surgical aspects are considered together with the practice of physical activity, with emphasis upon the differences between the various countries. Particular attention is paid to the Italian legislation regarding the certification to participate in competitive or non-competitive sport in such a population of patients. Great importance is given to pediatric cardiac rehabilitation programs which aim at improving the aerobic fitness of patients operated upon for complex congenital heart disease and at illustrating their own cardiovascular limitations so that they can perform physical exercise with the utmost safety.

Cardiac Surgical Procedures↗
PubMed2000

Clinical and cardiorespiratory assessment in children with Down syndrome without congenital heart disease.

OBJECTIVE: To assess the clinical and functional status of a young Down syndrome (DS) population without congenital heart disease. DESIGN: Prospective study of children with DS and control subjects. SETTING: Bambino Gesù Children's Hospital, Rome, Italy. PARTICIPANTS AND METHODS: Forty-two children with DS (mean +/- SD age, 9.8 +/- 3.6 years) underwent genetic, clinical, neuropsychological (IQ), and cardiorespiratory evaluation. Cardiorespiratory fitness was assessed with a treadmill test and a lung function test to determine forced vital capacity, first-second forced expiratory volume, and peak expiratory flow. Data were expressed as a percentage of the predicted values for control children. To assess cooperation during exercise testing, we devised a compliance scale assigning a score according to the subjects' ability to understand instructions, ability to walk and run as required, and need for vocal encouragement. RESULTS: Eighteen (43%) of 42 children with DS were obese, 10 (24%) were short, and 17 (40%) had microcephaly. On the Leiter International Performance Scale, 2 of 35 subjects had a normal IQ score (80-120); all others had low IQ scores (79 to <40). Five subjects did not undergo cardiorespiratory assessment. Eighteen of 37 subjects completed lung function tests: the results for 10 were unremarkable, and results from 8 revealed reduced forced vital capacity because of poor compliance. The subjects tested had low exercise tolerance (mean +/- SD tolerance percentage, 61% +/- 12%), mild tachycardia (maximal heart rate, 91% +/- 4%), and a mild hypertensive response (maximal blood pressure, 89% +/- 8%). Compliance scores correlated significantly with exercise time and age but not with IQ. CONCLUSIONS: Clinical and cardiorespiratory assessment is feasible in subjects with DS without congenital heart disease and should be useful in gauging their fitness level for safe physical activity.

Adolescent↗
PubMed2000

Ambulatory blood pressure monitoring in children with aortic coarctation and kidney transplantation.

BACKGROUND: Ambulatory blood pressure monitoring (ABPM) has been found to be of significant importance in clinical practice because numerous blood pressure (BP) measurements may be made throughout the 24-hour period. OBJECTIVE: To assess the clinical utility of ABPM in children with secondary hypertension. METHODS: We studied 37 patients (21 boys and 16 girls), with a mean age of 16.4 +/- 4.1 years, after kidney transplantation and 38 patients (27 boys and 11 girls), with a mean age of 10.2 +/- 2.1 years, after surgical correction of aortic coarctation. Data, expressed as mean +/- SD, were analyzed after dividing the patients into 4 groups. Group A consisted of 25 patients receiving antihypertensive therapy; group B included 12 patients not receiving antihypertensive therapy. Group C included 25 patients operated on before 3 years of age (8 +/- 7 months of age); group D included 13 patients operated on after 3 years of age (74 +/- 29 months of age). RESULTS: In groups A and B, casual BP measurement showed that 16 of 37 patients (43%) were hypertensive; 24-hour ABPM detected a larger number of patients who were hypertensive (23 of 37, 62%); there were 18 in group A and 5 in group B. In groups C and D, casual BP measurement identified 6 of 38 (15%) patients as hypertensive, whereas 24-hour ABPM again identified a higher number (13 of 38, 34%). CONCLUSIONS: Our findings confirm that 24-hour ABPM is more sensitive than casual BP in detecting abnormal BP in patients at high risk for secondary hypertension.

Adolescent↗
PubMed2000

Neuroregulation of growth hormone during exercise in children.

Physical exercise is an important physiological stimulus to growth hormone (GH) release in man. Many neurotransmitters are involved in GH regulation. We studied the effect of the cholinergic pathway on GH secretion induced by physical exercise. Particularly, we studied the effect of a cholinergic muscarinic agonist on GH-induced physical exercise, both in children and adults. Moreover, we investigated the refractoriness of GH secretion after a second physical exercise stimulus. Three different protocols were performed: 1) GH response to physical exercise in children and adults; 2) effect of pyridostigmine on exercise-induced GH secretion in children and adults; 3) GH response to two consecutive exercises in children and adults. Our data show that in children GH peak after physical exercise is higher than in adults. Pyridostigmine enhances GH release in children and in adults. Exercise stimulus was able to release GH in the second test only in children, while the refractory phase did not permit a new GH release in adults. The shift to a modality of neural control of GH secretion peculiar of adults is likely due to neuroregulatory mechanisms which may be partly dependent on long-term variation in hormonal milieu.

Adolescent↗
PubMed1999

The sae locus of Staphylococcus aureus encodes a two-component regulatory system.

Sae is a regulatory locus that activates the production of several exoproteins in Staphylococcus aureus. A 3.4-kb fragment of a S. aureus genomic library, screened with a probe adjacent to the transposon insertion of a sae::Tn551 mutant, was cloned into a bifunctional vector. This fragment was shown to carry the sae locus by restoration of exoprotein production in sae mutants. The sae locus was mapped to the SmaI-D fragment of the staphylococcal chromosome by pulse-field electrophoresis. Sequence analysis of the cloned fragment revealed the presence of two genes, designated saeR and saeS, encoding a response regulator and a histidine protein kinase, respectively, with high homology to other bacterial two-component regulatory systems.

Amino Acid Sequence↗
PubMed1999

Epstein-Barr virus infection and P53 expression in HIV-related oral large B cell lymphoma.

BACKGROUND: Head and neck non-Hodgkin's lymphomas in HIV positive patients are highly related with Epstein-Barr virus (EBV) infection. In general, viral agents can alter p53 protein levels by enhancing degradation of cellular p53 or by increasing its half-life by viral protein-p53 interaction. Moreover, it has been reported that modifications of p53 gene can modulate tumor cells' response to radio- and chemotherapy. METHODS: To assess a possible role of EBV infection, p53 protein deregulation, and p53 gene alterations in exons 5 to 8, we have studied six cases of HIV-related primary oral large B-cell lymphoma. We used in situ hybridization (ISH) for EBV-DNA and EBV-encoded nuclear RNA-1 (EBER-1), immunohistochemistry (IHC) for EBV latent membrane protein -1 (LMP-1) and p53 proteins expression, and single strand conformational polymorphism (SSCP) analysis to screen p53 gene mutations in exons 5 to 8. RESULTS: The EBV-DNA was present in all specimens, according to conventional DNA-ISH. No evidence for EBER-1 was found by ISH. The presence of EBV-DNA was correlated with the LMP-1 expression in all but one case. Moreover, p53 protein expression was negative in three cases and strongly positive in the others. However, mutational analysis of p53 gene in exons 5-8 showed no alteration. CONCLUSIONS: Our data may suggest that both EBV infection and LMP-1 expression may cause p53 loss of function even in the absence of p53 gene mutations, as assessed by SSCP. We speculate that the presence of EBV-infection and p53 protein deregulation may be responsible for radio- and chemotherapy resistance, by influencing apoptosis of cancer cells.

Adult↗
PubMed1999

Reduction of bcl-2 in T cells during immunosuppressive therapy in patients with severe juvenile onset systemic lupus erythematosus.

Overexpression of bcl-2 protein has been observed in the cytoplasm of T lymphocytes from adults with systemic lupus erythematosus (SLE). The aims of our study were to investigate the distribution of bcl-2 in T and B cells from patients affected with juvenile onset SLE (JSLE) and to monitor the modification of bcl-2 expression under immunosuppressive therapy. Thirty-two JSLE patients entered the study; 45 pathological and 16 healthy subjects were studied as controls. In SLE patients the disease activity was assessed using SLE disease activity index score. Bcl-2 expression was evaluated by cytofluorimetry. PCR analysis of t(14,18) translocation was performed from genomic DNA isolated from peripheral blood mononuclear cells. An increased bcl-2 expression both on cytoplasm and on cell surface of circulating T lymphocytes in JSLE patients with active disease was found. A variation, under pharmacological treatment, of protein expression during the course of the disease was observed. PCR analyses demonstrated that 14, 18 translocation was not associated with bcl-2 overexpression. Our data show a strong correlation between bcl-2 protein expression and disease activity and suggest an alteration of apoptotic regulation in JSLE patients.

Adolescent↗
PubMed1999

Tachycardias in children originating in the right ventricular outflow tract: lack of clinical features predicting the presence and severity of the histopathological substrate.

The aim was to determine whether the clinical features of tachycardias originating from the right ventricular outflow tract in children with an apparently normal heart could predict the presence and the severity of the histopathological substrate. Thirteen children (median age 6 years; range 6 months-12 years) with tachycardia originating from the right ventricular outflow tract of apparently normal hearts, were assessed by echocardiography, heart catheterization with angiography, endomyocardial biopsy (13 patients) and magnetic resonance imaging (MRI) (nine patients). Tachycardia was symptomatic in six and sustained in nine. Endomyocardial biopsy and MRI revealed acute myocarditis in five patients (38%), fatty infiltration of the right ventricle in two (15%), and minor histologic abnormalities in three (23%). Myocarditis was diagnosed in three of nine patients with sustained ventricular tachycardia, as opposed to two of four with non-sustained tachycardia (p = NS); in three of six symptomatic versus two of seven asymptomatic patients (p = NS); and in two of eight patients in whom ventricular tachycardia was induced during exercise testing as opposed to one of three in which it was not inducible (p = NS). A histopathological substrate was found in six of nine patients with sustained ventricular tachycardia, and in all four with non-sustained tachycardia (p = NS); in five of six patients with symptoms versus five of seven asymptomatic patients (p = NS); and in five of eight with inducible ventricular tachycardia during exercise testing versus all three in whom it was not inducible (p = NS). The mean rate of tachycardia was 184+/-39 beats min(-1) in patients with myocarditis, as opposed to 171+/-48 in patients without myocarditis (p = NS); and 163+/-33 in patients with a histopathological substrate compared with 210+/-65 in patients without a histopathological substrate (p = NS). It is concluded that a histopathological substrate is present in the greater majority of children affected by the so-called right ventricular outflow tract tachycardia, but that the clinical features of the tachycardia do not predict the presence and the severity of this histopathological substrate.

Biopsy↗