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Biomedical subjects

A Luciani

Publications and source records attributed to A Luciani.

At least 19 recordsLinked to original sources
PubMed2006

Synthesis and characterization of macroporous poly(ethylene glycol)-based hydrogels for tissue engineering application.

Peptide activated poly(ethylene glycol) (PEG)-based hydrogels have received wide attention as material for tissue engineering application. However, the close structure of these materials may pose severe barriers to tissue invasion and nutrient transport. The aim of this work was to synthesize highly interconnected macroporous PEG hydrogels, suitable for use as tissue engineering scaffolds, by combining the photocrosslinking reaction with a foaming process. In particular, various porous samples, differing for both the polymer molecular weight and concentration in the starting precursor solution, have been prepared and characterized by means of scanning electron microscopy and mercury porosimetry. Moreover, water swelling properties have been evaluated and compared with those of the conventional nonporous ones, by performing both equilibrium and kinetic swelling measurements in distilled water. Results indicated that foamed hydrogels display a well-interconnected porous network, suitable for tissue invasion and free molecular trafficking within them. Pores dimension as well as swelling rate can be modulated by polymer concentrations and bubbling agent composition in the precursor solution.

Biocompatible Materials↗
PubMed2006

Americium in the beagle dog: biokinetic and dosimetric model.

A biokinetic model of the systemic distribution of americium in the beagle dog is presented. The model is based on a previous biokinetic model of plutonium. The data sets used for the development of the model were the measurements of excreted activity (urine and feces) and organ burdens (skeleton, liver, and other soft tissues) for different levels of initial injected activity. In developing the model, the compartmental structure of the skeleton of the plutonium model was adopted, and only the numerical values of parameters were adapted. The model well describes the fractions of americium in the skeleton, liver, and soft tissues and the total fraction excreted in urine and feces. The tuning of the liver clearance parameter provides a realistic description of the change in the partitioning between liver and skeleton for different injection levels. The most significant features of the biokinetics and dosimetry of americium and plutonium in beagles are compared. The total fractions of the clearance to the skeleton and the liver are roughly equal to the value for plutonium, but the partitioning of americium between these organs is reversed with respect to the partitioning of plutonium. 241Am doses to liver and skeleton are similar to 239Pu doses, owing to some counteracting factors. For the highest injection level, the liver mass is dependent on the time post injection. For the skeletal tissues, the dose to the cortical endosteum by far exceeds the dose to the trabecular endosteum and the red marrow. The model provides the basis for statistical survival analyses and risk estimates.

Americium↗
PubMed2005

Evaluation of tumoral enhancement by superparamagnetic iron oxide particles: comparative studies with ferumoxtran and anionic iron oxide nanoparticles.

This study was designed to compare tumor enhancement by superparamagnetic iron oxide particles, using anionic iron oxide nanoparticles (AP) and ferumoxtran. In vitro, relaxometry and media with increasing complexity were used to assess the changes in r2 relaxivity due to cellular internalization. In vivo, 26 mice with subcutaneously implanted tumors were imaged for 24 h after injection of particles to describe kinetics of enhancement using T1 spin echo, T2 spin echo, and T2 fast spin echo sequences. In vitro, the r2 relaxivity decreased over time (0-4 h) when AP were uptaken by cells. The loss of r2 relaxivity was less pronounced with long (Hahn Echo) than short (Carr-Purcell-Meiboom-Gill) echo time sequences. In vivo, our results with ferumoxtran showed an early T2 peak (1 h), suggesting intravascular particles and a second peak in T1 (12 h), suggesting intrainterstitial accumulation of particles. With AP, the late peak (24 h) suggested an intracellular accumulation of particles. In vitro, anionic iron oxide nanoparticles are suitable for cellular labeling due to a high cellular uptake. Conversely, in vivo, ferumoxtran is suitable for passive targeting of tumors due to a favorable biodistribution.

Adenocarcinoma↗
PubMed2004

Glucagon-like peptide 1 (GLP-1) secretion and plasma dipeptidyl peptidase IV (DPP-IV) activity in morbidly obese patients undergoing biliopancreatic diversion.

BACKGROUND: The physiological inhibitory control of glucagon-like Peptide 1 (GLP-1) on gastric emptying and the contribution of this peptide in the regulation of food intake as a satiety factor suggest that impaired secretion and/or activity of GLP-1 may be involved in the pathogenesis of obesity. We investigated food-mediated GLP-1 secretion as well as plasma activity of dipeptidyl-peptidase IV (DPP-IV), the enzyme responsible for rapid inactivation of the circulating peptide, in morbidly obese patients, before and after weight loss resulting from biliopancreatic diversion. METHODS: Twenty-two morbidly obese non-diabetic patients (BMI = 47.5 +/- 1.8) and 9 age-matched healthy volunteers were studied. A mixed meal (700 kcal) was administered to all subjects and blood samples were collected at 0, 15, 30, 60, 120 min for the determination of circulating glucose, insulin, GLP-1 (7 - 36 amide) concentrations and plasma DPP-IV activity. The patients repeated the test meal after 50 % overweight reduction resulting from surgical treatment (BMI = 33.8 +/- 1.1). RESULTS: While nutrient ingestion significantly increased plasma GLP-1 levels in the control group (30', 60': p < 0.01), the test-meal failed to modify basal peptide values in the obese patients, and an overall reduction in circulating GLP-1 occurred during the observation period (p < 0.001). Plasma DPP-IV activity in the same patients resulted as being significantly higher than controls, both at fasting and in response to the meal (p < 0.05). With respect to preoperative values, an overall increase in circulating GLP-1 levels occurred in all patients following biliopancreatic diversion (p < 0.001). Plasma DPP-IV activity, on the other hand, continued to be abnormally increased, even after considerable weight loss (p < 0.05 vs. controls). CONCLUSIONS: First: In morbid obesity, the accelerated inactivation of circulating GLP-1 could at least partially account for plasma peptide levels lower than normal, the defective availability of such a satiety factor possibly contributing to eating behaviour abnormalities; Second: plasma DPP-IV hyperactivity in the obese did not seem to be affected by the overweight degree, the increase in postoperative GLP-1 levels mainly resulting from hyperstimulation of GLP-1 secretory cells due to surgical manipulation of gastrointestinal tract. If the abnormally accelerated degradation of GLP-1 in obesity is confirmed, selective DPP-IV inhibitors could actually represent an ideal approach to obesity management.

Adult↗
PubMed2003

Sensitivity analysis techniques applied to a revised model of molybdenum biokinetics.

A revised model of molybdenum biokinetics in humans was recently developed on the basis of experimental data gathered in specific investigations conducted with stable tracers. The model can be used for radiation protection purposes, and it is also a suitable working tool for designing new investigations aimed at further improvements to the model. For the latter goal, a sensitivity analysis was performed in order to determine the most significant model parameters in relation to output measurements performed in studies of molybdenum metabolism. A typical sensitivity analysis approach was adopted, considering the effects in variation of model parameters on the time courses of model outputs such as urinary excretion and blood clearance. A recent new sensitivity technique was considered too, based on the calculation of the so-called generalised sensitivity functions. This combines the sensitivities of the model output with respect to model parameters (as in the typical sensitivity analysis method), with the sensitivities of parameter estimates with respect to changes in model outputs. The results obtained in this analysis suggests that data collected in the first 7 h are critical for the definition of the process of blood clearance and related parameters, whereas reliable information at later times is required for a proper characterisation of urinary excretion.

Body Burden↗
PubMed2003

Uncertainty analysis of the urinary excretion of plutonium.

A quantitative estimate of the uncertainty of the urinary excretion of plutonium predicted by available biokinetic models is provided. Urinary excretion is primarily considered here because the monitoring of internal contamination of plutonium mainly relies on measurements of activity in urine samples. A previous paper has identified the most significant transfer rates for urinary plutonium excretion following an acute intake. That analysis is used here as a screening method to reduce the number of model parameters to be considered. A log-normal distribution was assumed for the probability distribution of the model parameters. The spread of the values, represented by the geometric standard deviation (GSD), is explicitly calculated, as few indications of the range of variation of systemic transfer rates are available. Different values for the GSD were considered. Assuming a certain GSD for all the systemic rate constants, random values of the rates were generated (by means of a Monte Carlo simulation with a Latin hypercube sampling scheme) and the resulting predictions of urine bioassay measurements were calculated. The comparison of the mean and variance of the predictions with the available data from several studies performed on different subjects provides information about the GSD of model parameters that represents the intersubject variation of transfer parameters.

Animals↗
PubMed2003

Italian intercomparison exercise on internal dose assessment.

In 2001, the Radiation Protection Institute of ENEA promoted an Italian intercomparison exercise on internal dose assessment addressed to the qualified experts in radiation protection, following the coming into force in Italian law of the EURATOM 96/29 Directive. Five case studies of occupational exposure related to the Italian situation are used. The considered radioisotopes are: 60Co, 89Sr, 125I, 131I, and 222Rn + NORM (238U-235U-232Th). Data related to WBC, thyroid and urine excretion measurements, as well as radionuclide air concentration in the workplace, are provided to the participants. The results related to medical, industrial and Rn occupational exposure are well represented as means of log-normal distributions with values of the geometric standard deviation less than 2. A wider spread of results is present for the evaluation of occupational exposure to NORM.

Benchmarking↗
PubMed2002

Evidence for early impairment of glucagon-like peptide 1-induced insulin secretion in human type 2 (non insulin-dependent) diabetes.

UNLABELLED: To investigate a possible role of an enteroinsular axis involvement in the pathogenesis of type 2 diabetes, plasma glucagon-like peptide 1 (GLP-1) 7-36 amide response to nutrient ingestion was evaluated in type 2 diabetics affected by different degrees of beta-cell dysfunction. METHODS: 14 patients on oral hypoglycaemic treatment (group A: HbA1C = 8.1 +/- 1.8 %) and 11 age-matched diabetic patients on diet only (group B: HbA1C = 6.4 +/- 0.9) participated in the study. 10 healthy volunteers were studied as controls. In the postabsorptive state, a mixed meal (700 kCal) was administered to all subjects, and blood samples were regularly collected up to 180' for plasma glucose, insulin, glucagon, and GLP-1 determination. RESULTS: In the control group, the test meal induced a significant increase in plasma GLP-1 at 30' and 60' (p < 0.01); the peptide concentrations then returning toward basal levels. beta-cell function estimation by HOMA score confirmed a more advanced involvement in group A than in group B (p < 0.01). In contrast, the insulin resistance degree showed a similar result in the two groups (HOMA-R). In group A, first-phase postprandial insulin secretion (0 - 60') resulted, as expected, in being significantly reduced compared to healthy subjects (p < 0.001). In the same patients the mean fasting GLP-1 value was similar to controls, but the meal failed to increase plasma peptide levels, which even tended to decrease during the test (p < 0.01). In group B, food-mediated early insulin secretion was higher than in group A (p < 0.001), although significantly reduced when compared to controls (p < 0.01). Like group A, no GLP-1 response to food ingestion occurred in group B patients in spite of maintained basal peptide secretion. Whereas the test-meal did not significantly modify plasma glucagon levels in the control group, glucagon concentrations increased at 30' and 60' in both diabetic groups (p < 0.01). CONCLUSIONS: 1) The functional integrity of GLP-1 cells results as being seriously impaired even in the condition of mild diabetes; 2) the early peptide failure could contribute to the development of beta-cell deterioration which characterizes overt type 2 diabetes.

Aged↗
PubMed2002

Focal nodular hyperplasia of the liver in men: is presentation the same in men and women?

BACKGROUND: Focal nodular hyperplasia (FNH) of the liver is a benign hepatic lesion relatively common in women. No studies specifically designed to describe the presentation and imaging findings in males have been published. AIMS: The aims of this study were: (a) to describe the clinical and imaging findings in 18 men with FNH, and (b) to compare these data with those observed in 216 women with FNH observed during the same nine year period. PATIENTS AND METHODS: According to a final diagnosis of FNH assessed either by pathological examination or by magnetic resonance (MR), the medical charts of 18 men with FNH observed at our institution were reviewed. In order to compare clinical and MR presentations, the files of 216 women with a total of 291 FNH lesions, investigated during the same nine year period, were reviewed. RESULTS: Eighteen FNH lesions, with a mean diameter of 37.5 mm, were demonstrated in the 18 male patients. A total of 291 lesions with a mean diameter of 63.4 mm were comparatively demonstrated in 216 female patients. Mean age at diagnosis was significantly higher in men (p<0.01) and mean FNH size was significantly smaller in men (p<0.001). Surgery was more frequently performed in men (72.2%) than in women (16.7%) (p<0.001). CONCLUSIONS: Our data indicate that FNH is rare in men and that the lesions are smaller and more often atypical than those in women.

Abdominal Pain↗
PubMed2001

Sensitivity analysis of the urinary excretion of plutonium.

The transfer parameters of a new age-related model for plutonium metabolism, which have the largest influence on urinary excretion, are determined by applying a sensitivity analysis and assuming a direct uptake into blood. Realistic cases of contamination via ingestion and inhalation were considered as well and sensitivity coefficients for non-systemic parameters were calculated. The most important parameters in relation to the path of intake are identified and the effects of the modifying factors proposed by the ICRP in the case of alteration of respiratory tract physiology are briefly examined.

Absorption↗
PubMed2001

Catheter-related upper extremity deep venous thrombosis in cancer patients: a prospective study based on Doppler US.

PURPOSE: This prospective study extending for more than 3 years had two objectives: (a) to use Doppler ultrasonography (US) to estimate the incidence of asymptomatic catheter-related upper extremity deep venous thrombosis (DVT) in a large population and (b) to study the effect of the catheter position as an individual risk factor for catheter-related DVT. MATERIALS AND METHODS: Between October 1995 and June 1998, a total of 145 patients who had oropharyngeal tract cancer and who were fitted with the same totally implantable central venous catheters (CVCs) were included in the study. Follow-up included (a) estimation of the position of each catheter tip on a chest radiograph obtained immediately after surgery and (b) regular monthly Doppler US screening for catheter-related DVT. RESULTS: Seventeen patients developed catheter-related DVT; 13 of them were asymptomatic. The mean interval between CVC implantation and detection of thrombosis was 42.2 days. Correct positioning of the distal catheter tip was associated with a significantly lower rate of catheter-related DVT. Only five of 87 patients with a correctly positioned distal catheter tip (ie, either in the superior vena cava or at the junction between the right atrium and the superior vena cava) developed thrombosis, compared with 12 of 26 patients with a misplaced catheter (P <.001). The side on which the CVC was implanted did not influence the catheter-related DVT rate. CONCLUSION: The rate of asymptomatic catheter-related DVT is high and could be lowered with correct initial CVC positioning.

Adult↗
PubMed2001

Spontaneous closure of dural arteriovenous fistulas: report of three cases and review of the literature.

SUMMARY: Three cases of spontaneously closing dural arteriovenous fistulas (AVFs) are presented, and 11 previously published cases are reviewed. On the basis of clinical and angiographic data, two types of spontaneously regressing dural AVFs are distinguished: posttraumatic and spontaneous. In all cases, the explanation for spontaneous closure is unknown. Some authors have hypothesized that the thrombosis of the draining sinus could be involved. We report three cases of spontaneous dural AVF closure with conservation of sinus patency.

Adult↗
PubMed2000

Verification and modification of the ICRP-67 model for plutonium dose calculation.

On the basis of the available data and empirical expressions for the plutonium excretion after injection, an age-related compartmental model has been developed. It provides a better agreement with measured urinary excretion data than the current ICRP 67 model. Moreover, the revised model avoids unphysiological assumptions such as the transfer of activity from soft tissue to urinary bladder, that were part of the ICRP model. The new predictions of the activity in feces and in blood after an injection are closer to the available data than the ICRP 67 estimations and there is also a good agreement with the partitioning of plutonium between skeleton and liver obtained from different autopsy studies. Furthermore, the urinary excretion estimated by the improved model has been checked using some data from occupationally exposed individuals. As the plutonium uptake in these workers occurred by inhalation, the improved model and the ICRP 67 model were compared by connecting them to the ICRP 66 respiratory tract model. The improved model consistently yields a better agreement with the measured excretion and higher estimations of intake than the ICRP 67 model.

Body Burden↗