Time-resolved X-ray powder diffraction on a three-way catalyst at the GILDA beamline.

Time-resolved X-ray diffraction experiments carried out at the beamline BM08-GILDA of ESRF allowed a study of the structural modifications taking place in a Pt/ceria-zirconia catalyst while the CO oxidation reaction was in progress. The capillary tube in which the sample is stored acts effectively as a chemical microreactor that ensures homogeneity of the sample treatments and minimization of diffusion effects. During the flowing of the reactant CO/He mixture, the investigated catalyst undergoes a fast Ce(IV)-Ce(III) partial reduction that involves the release of one O atom for every two reduced Ce cations. Because Ce(III) has a larger ionic radius than Ce(IV), the structural modification produces an increase of the lattice constant of the ceria-zirconia mixed oxide, and this increase is monitored by the translating imaging-plate device implemented at GILDA. The CO(2) resulting from the oxidation of the fluxed CO is monitored by a quadrupole mass spectrometer during the recording of the time-resolved X-ray diffraction pattern. The chemical and structural information was combined to show that the CO(2) yield is nearly constant until the catalytic system can provide oxygen for the reaction, while the structural rearrangement of the catalyst is delayed with respect to the switching on of the CO/He flux. After this induction time, during which CO(2) is produced with no structural modification of the catalyst, a fast increase of the lattice constant takes place.

[Lactitol in chronic idiopathic constipation in children]. / Il lattitolo nella stipsi cronica idiopatica del bambino.

Fifty-one children affected by chronic idiopathic constipation (23 males, 28 females), ranging in age from 8 months to 16 years were enrolled in the study; 42 completed the trial. The patients were divided into two groups: Group A: 19 children treated with lactitol (250-400 mg/kg/day); Group B:23 patients treated with lactulose (500-750 mg/kg/day). Parents filled a questionnaire concerning clinical response to therapy for a period of 30 days. In 17 Group A children and in 17 Group B children orocecal transit time using H2 Breath Test with lactulose was performed. A statistically significant increase of week stool frequency was found after treatment both with lactitol or lactulose (p < 0.001). Nevertheless Group B patients complained abdominal pain (p < 0.005) and flatus (p < 0.001) more frequently. Other adverse reactions, such as vomiting and meteorism, were more frequent in Group B patients (n.s.). In addition patients treated with lactitol found that sugar as more palatable and had a better compliance to the therapy. Orocecal transit time did not show statistically significant differences after the therapy with both these sugars, indicating that the activity of lactulose and lactitol occurs in the colon and that small bowel functions are not affected by a previous therapy with these sugars. In conclusion, our study demonstrate that lactitol, because of the less number of side effects compared to lactulose, should be considered as an useful agent in the treatment of chronic idiopathic constipation in childhood.

[High incidence of Helicobacter pylori infections in an endoscopic pediatric patient series]. / Elevata incidenza di infezione da Helicobacter pylori in una casistica endoscopica pediatrica.

We evaluated in children with abdominal complaints the prevalence of Helicobacter pylori gastric and duodenal colonization and the histological features of gastric and duodenal mucosae. Fifty patients, aged 1-17 years, underwent upper endoscopy for recurrent abdominal pain, vomiting and/or gastrointestinal bleeding. With serological, bacteriological and/or histological methods twenty-eight children were demonstrated to be Helicobacter pylori-positive. No statistically significant differences were observed with regard to age, sex and indication to perform endoscopy. Eighty-two percent of Helicobacter pylori-positive patients had gastritis and/or duodenitis. The Helicobacter pylori-positive children had higher Helicobacter pylori specific IgG levels than the Helicobacter pylori-negative ones (p < 0.001). No statistically significant differences were found between Helicobacter pylori-positive and Helicobacter pylori-negative subjects, for gastrin and pepsinogen I. Since the frequency of Helicobacter pylori infection in children with gastrointestinal complaints is high, in patients undergoing upper endoscopy, the sistematical examination of bioptic samples for bacteriological and histologic procedures is of great importance.

[Prevalence of lactose malabsorption in Roman school children. A H2 breath test study using a cow's milk]. / Prevalenza del malàssorbimento del lattosio in una popolazione scolastica romana. Un'indagine mediante H2 breath test con latte vaccino.

The aim of this study was to evaluate the prevalence of lactose malabsorption in a population of 75 (43 males, 32 females) apparently healthy school-children using the H2 breath test with cow's milk. The children, ranging in age from 8 years and 6 months to 15 years and 2 months (mean: 11 years, 7 months) were divided into 2 age groups: Group I (no. = 26): age < 11 years and Group II (no. = 49): age > 11 years. After on overnight fasting, lasting at least 8 hours, samples of expired air were collected at 0 time and at 30-min intervals following the administration of 250 ml cow's milk for a total time of 3 hours. The H2 breath concentration was then measured by gas chromatography (Micro-Lyzer Quintron Instruments Company mod. 12). A net rise of more than 20 ppm H2 was considered as lactose malabsorption. Subjects with symptoms such as excessive flatulence, abdominal pain, or diarrhoea, were considered as lactose intolerant. Two-hundred and 50 ml of cow's milk (12 g of lactose) was considered a more physiological vehicle than the traditional lactose aqueous solution. The examined children, all on free diet, showed a fasting alveolar from 0 to 43 ppm (mean +/- SD = 7.9 +/- 7.6). Sixty-six children out of 70 (93.3%), who completed the test had a total absorption of lactose. Two out of 4 children with lactose malabsorption originated from areas (East Africa and Central America), where a high incidence of this metabolic disorder is a characteristic findings.(ABSTRACT TRUNCATED AT 250 WORDS)

[The evaluation of body composition in children by anthropometry and impedance measurement]. / Valutazione della composizione corporea nel bambino mediante antropometria ed impedenziometria.

Several anthropometric parameters (weight, height, thickness skinfolds, and body circumferences) together with the bioelectric impedance (BIA) were measured in a group of 407 healthy prepuberal children (205 males, mean age +/- SD: 6.8 +/- 1.6 years; 202 females, mean age +/- SD: 6.6 +/- 1.6 years) who did not practice any competitive sport. The group was divided into six weight classes (underweight to obese 3). The average values of the anthropometric data, BIA, FM (which is derived from the thickness skinfolds and BIA), TBW (derived from BIA), AFA and AMA (both derived from the forearm circumference and triceps skinfold) were all evaluated in relation to sex and weight classes. The average values of all the measured thickness skinfolds, FM and AFA were higher in the females. When considering the body circumferences, only the wrist circumference showed a statistically significant difference between sexes, being higher in males. In contrast both the rates waist/hips circumferences and waist/thigh circumferences were higher in males. As far as the BIA and FM average values is concerned, these were higher in females. The average value of FM derived from measuring the thickness skinfolds (males = 17.65 +/- 4.89%: females = 23.81 +/- 4.72% of body weight) proved higher than that one derived from BIA (males = 17 +/- 9.02%; females = 19.27 +/- 9.18%). The analysis of anthropometric and BIA data in relation to the weight classes showed significant variations of the mean values, except the rates waist/hips circumferences and waist/thigh circumferences. Therefore our data seem to exclude the presence of any difference of the fat distribution between sexes in paediatric age.(ABSTRACT TRUNCATED AT 250 WORDS)