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Biomedical subjects

C Bruni

Publications and source records attributed to C Bruni.

At least 19 recordsLinked to original sources
PubMed2005

Advection-induced spectrotemporal defects in a free-electron laser.

We evidence numerically and experimentally that advection can induce spectrotemporal defects in a system presenting a localized structure. Those defects in the spectrum are associated with the breakings induced by the drift of the localized solution. The results are based on simulations and experiments performed on the super-ACO free-electron laser. However, we show that this instability can be generalized using a real Ginzburg-Landau equation with (i) advection and (ii) a finite-size supercritical region.

Journal Article↗
PubMed2004

Suppression of the pulsed regimes appearing in free-electron lasers using feedback control of an unstable stationary state.

We show that the pulsed regimes observed in free-electron lasers (FELs) can be suppressed using feedback control. By applying tiny parameter perturbations, the feedback allows to keep the systems onto a stationary state that is naturally existing in phase space, but is usually inaccessible because of its unstable nature. We test this method numerically on a master equation derived from the classical iterative model. Then we present the experimental results obtained on the super-ACO FEL. This method is in principle directly applicable to the other free-electron lasers, whose instabilities have a dynamical (deterministic) origin.

Journal Article↗
PubMed2004

Saturation and electron-beam lifetime in a storage ring free-electron laser.

We present a phenomenological treatment of free-electron laser storage ring saturation dynamics. The model includes longitudinal instabilities, Touschek intrabeam scattering, and nonzero off-energy-function contributions. The model predictions are compared with Super ACO experimental results and the agreement is shown to be satisfactory.

Journal Article↗
PubMed2003

VO2, VCO2, and RQ in a respiratory chamber: accurate estimation based on a new mathematical model using the Kalman-Bucy method.

A respiratory chamber is used for monitoring O(2) consumption (Vo(2)), CO(2) production (Vco(2)), and respiratory quotient (RQ) in humans, enabling long term (24-h) observation under free-living conditions. Computation of Vo(2) and Vco(2) is currently done by inversion of a mass balance equation, with no consideration of measurement errors and other uncertainties. To improve the accuracy of the results, a new mathematical model is suggested in the present study explicitly accounting for the presence of such uncertainties and error sources and enabling the use of optimal filtering methods. Experiments have been realized, injecting known gas quantities and estimating them using the proposed mathematical model and the Kalman-Bucy (KB) estimation method. The estimates obtained reproduce the known production rates much better than standard methods; in particular, the mean error when fitting the known production rates is 15.6 +/- 0.9 vs. 186 +/- 36 ml/min obtained using a conventional method. Experiments with 11 humans were carried out as well, where Vo(2) and Vco(2) were estimated. The variance of the estimation errors, produced by the KB method, appears relatively small and rapidly convergent. Spectral analysis is performed to assess the residual noise content in the estimates, revealing large improvement: 2.9 +/- 0.8 vs. 3,440 +/- 824 (ml/min)(2) and 1.8 +/- 0.5 vs. 2,057 +/- 532 (ml/min)(2), respectively, for Vo(2) and Vco(2) estimates. Consequently, the accuracy of the computed RQ is also highly improved (0.3 x 10(-4) vs. 800 x 10(-4)). The presented study demonstrates the validity of the proposed model and the improvement in the results when using a KB estimation method to resolve it.

Carbon Dioxide↗
PubMed2003

Steady state of a fully detuned storage-ring free-electron laser.

This paper gives an analytical description of the stationary regime of a storage-ring free-electron laser in the presence of the maximum detuning (compatible with the laser onset) between the laser pulse and the electron beam when they pass and interact in the optical cavity. In this condition, the conservation of the first moments of the laser intensity distribution allows one to express the peak gain of the light amplification process and the maximum detuning as a function of system parameters that are directly measurable. These theoretical results are compared with experiments performed on the Super-ACO free-electron laser.

Journal Article↗
PubMed2002

Spontaneous and forced non-linear oscillations in heart period: role of the sino-atrial node.

The aim of this study is to investigate whether and to which extent the non-linearity of the sino-atrial node contributes to the complex interactions between autonomic control and heart period. A non-linear model of the autonomic control on the sino-atrial node has been analyzed under particular experimental conditions: the autonomic nervous system was forced to act at established frequencies, by a controlled breathing procedure and a non-invasive periodic modulation of carotid baroreceptors. We quantify the non-linear coupling between the stimuli and both the experimental and the simulated heart period fluctuations by using the recurrence plot quantification analysis. Our results show that the non-linear interaction between external stimuli and heart period fluctuations is due to a certain extent to the non-linear features of the sino-atrial node.

Biophysical Phenomena↗
PubMed1993

A stochastic model for cell debris in flow cytometry.

An important problem in analyzing flow cytometry DNA measurements, especially for tumor samples, is the presence of background noise, mainly resulting from cellular debris. Several models have been proposed for subtracting this contribution from DNA content histograms. In the present paper we propose a model for background debris distribution based on a specific mechanism for the DNA fragmentation process of the cell nucleus. In particular, we suggest that the fragmentation is more likely to occur in the sites which are closer to the end points of the DNA chain. This accounts for the observed higher frequency of small-sized fragments in experimental DNA distribution. The proposed model depends on two parameters describing the intensity and the shape of the background. It has been successfully validated against four series of experimental data of DNA distribution with increasing level of background.

Cell Fractionation↗
PubMed1987

[Tiropramide chlorhydrate in premedication for endoscopic retrograde cholangiopancreatography and its effects on the motor activity of Oddi's sphincter].

The activity of tiropramide chlorhydrate in the pre-medication for the endoscopical examinations has been evaluated. In particular ERCP has been studied considering as parameters the timing of the different stages of the examination and the activity of Oddi's sphincter. At the end of endoscopy the pressure of the sphincterial region was measured a 3-way miniature catheter. Patients included in the study were divided into two different groups: group A treated with tiropramide chlorhydrate and diazepam vs group B treated only with diazepam. The group with patients pre-medicated with tiropramide chlorhydrate presented a significant reduction in the timing of the different stages of endoscopy. Endoscopy was better tolerated. Manometry showed an antispastic action of the drug without side effects. An important reduction of the degree and duration of the sphincterial phase activity, with a possible improvement of biliary defluxion into the duodenum, was observed.

Adult↗
PubMed1985

Validation of a mathematical procedure for computer analysis of flow cytometric DNA data in human tumors.

The determination of tritiated thymidine labeling index and the percentage of cells with S phase DNA content was performed on cell suspensions obtained from 69 patients with non-Hodgkin's lymphoma. The distributions of cells in the cell cycle by computer analysis of flow cytometric data were obtained by two mathematical procedures: the widely adopted Fried model and a new one proposed by Bruni et al. A significant agreement was observed by checking the Spearman index (rs) between the percentages of cells in the different cell cycle phases (G0/1, rs = 0.76; S, rs = 0.60; and G2 + M, rs = 0.43; p less than 0.001) determined by the two procedures. Similarly, a good correlation was observed between the labeling index (LI) and the S phase values obtained by the Fried (rs = 0.45, p less than 0.001) and Bruni (rs = 0.69, p less than 0.001) models, but with a higher agreement for the latter one. The S phase by the Bruni model was also superior in predicting LI: in fact, by employing the S cutoff value of 12%, a better agreement between low LI and low S phase or high LI and high S phase was observed with the Bruni procedure (90%) than with the Fried model (72%). Finally, the analysis of the prognostic significance of the different kinetic variables confirmed the prognostic relevance of LI at any time; the S phase percentage as determined by Bruni et al. was discriminant of survival only at shorter times, and no prognostic significance could be ascribed to S phase according to the Fried procedure.

Adult↗
PubMed1984

Analysis of DNA distributions from flow cytometry. Validation of an automatic procedure against simulated data.

A recently proposed automatic procedure for analyzing DNA distribution from flow cytometric data is extensively tested against simulated data. After a discussion of the procedure itself and of the simulation program, the results obtained are reported. They are evidence of the reliability of the procedure in extracting the proper underlying DNA distribution from sets of data obtained under various simulated instances. The different sources of error are then analyzed, along with their quantitative effects on the fit of the fluorescence histogram.

Computers↗
PubMed1983

On the inverse problem in flow cytometry recovering DNA distribution from FMF data.

The problem of recovering DNA distribution from cytofluorometric experimental data was investigated. Theoretical analysis led to a convenient formulation of the problem and to uniqueness results for its solution. A minimization algorithm has been implemented to get the optimal estimate of G1, S, G2, and M phase percentages. This algorithm was tested in some experimental cases.

Animals↗
PubMed1982

A case of ectopic ACTH syndrome: diagnostic difficulties caused by intermittent hormone secretion.

A patient with a thymic carcinoid tumour causing ectopic ACTH syndrome is presented. The case illustrates the rapid development of the clinical and laboratory findings often associated with ectopic secretion of ACTH, including severe proximal myopathy, emotional lability, and hypokalaemic alkalosis. Interpretation of conventional tests of pituitary-adrenal function was complicated by intermittent secretion of ACTH by the tumour. The results of selective venous sampling for ACTH ruled out pituitary ACTH hypersecretion and were suggestive of a thymic source; computerized tomography of the chest localized the tumour. In vivo and in vitro investigations confirmed excessive ACTH production by the tumour, and surgical resection plus radiotherapy has resulted in resolution of the syndrome. The diagnostic problems created by intermittent secretion of ACTH by these tumours and the pre-operative and post-operative medical management of these patients are discussed.

17-Hydroxycorticosteroids↗
PubMed1980

New fine structural features of cardiac rhabdomyoma: report of a case.

Electron microscopy of a cardiac rhabdomyoma revealed two varieties of cells: (1) typical "spider cells' characterized by few myofibrils and large aggregates of glycogen particles free in the cytoplasm; and (2) cells with more myofibrils, less glycogen, and glycogen within membrane-limited vacuoles. These differences in myofibril development and glycogen content represent two succeeding stages in the early maturation of normal cardiocytes. The vacuoles containing glycogen were interpreted as autophagic and, consequently, active in the glycogen decrease typical of normal maturing cardiocytes. Rhabdomyoma cells did not show the structures, e.g., T system, characteristic of the late normal heart development. This study supports the theory that arrested cardiocyte maturation is a factor in the pathogenesis of cardiac rhabdomyoma.

Female↗
PubMed1979

A perspective for pediatric surgeons: chronic idiopathic intestinal pseudoobstruction.

Chronic idiopathic intestinal pseudoobstruction (CIIP) is a disorder of alimentary tract motility with onset of symptoms in adolescence or young adulthood, characterized by recurring attacks of abdominal pain, distention, vomiting, and constipation often leading to malnutrition and death. Starting with an adolescent patient, treated for a succession of life-threatening attacks of pseudoobstruction, the authors have identified CIIP in four generations of a Virginia family. Studies show characteristic dilation and diminished motility of the esophagus and intestine. Surgery's role in CIIP is palliative, and operation should only be offered when medical measures have failed to control symptoms.

Adolescent↗
PubMed1975

Fine structure of dividing cells and of nondividing, differentiating cells of nickel sulfide-induced rhabdomyosarcomas.

Cells of nickel sulfide-induced rhabdomyosarcomas were studied with the electron microscope. Cells in the proliferative compartment were mononucleate and exhibited neither myofilaments nor other features of normal muscle cell differentiation. Cells in the nonproliferative compartment had myofilaments and differentiated similarly to the normal fetal and early postnatal muscle cells. The tumor cells did not differentiate beyond the initial stage of formation of triads and of the smooth endoplasmic reticulum. Transitional forms between undifferentiated and differentiated tumor cells were observed. Only a fraction of the progeny of the dividing cells seemed to differentiate; the remaining fraction did not and remained in the proliferative cell compartment as stem cells. The ratio between these cells and the descendants of the dividing cells that, by differentiation, became part of the nonproliferative cell compartment was a factor in the growth of the rhabdomyosarcomas. The pattern of fetal differentiation of the rhabdomyosarcomas was analogous to that of diethylnitrosamine-induced hepatomas studied previously in this laboratory.

Animals↗