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Biomedical subjects

A Petrucci

Publications and source records attributed to A Petrucci.

15 recordsLinked to original sources
PubMed2006

Charge collection efficiency in ionization chambers exposed to electron beams with high dose per pulse.

The correction for charge recombination was determined for different plane-parallel ionization chambers exposed to clinical electron beams with low and high dose per pulse, respectively. The electron energy was nearly the same (about 7 and 9 MeV) for any of the beams used. Boag's two-voltage analysis (TVA) was used to determine the correction for ion losses, k(s), relevant to each chamber considered. The presence of free electrons in the air of the chamber cavity was accounted for in determining k(s) by TVA. The determination of k(s) was made on the basis of the models for ion recombination proposed in past years by Boag, Hochhäuser and Balk to account for the presence of free electrons. The absorbed dose measurements in both low-dose-per-pulse (less than 0.3 mGy per pulse) and high-dose-per-pulse (20-120 mGy per pulse range) electron beams were compared with ferrous sulphate chemical dosimetry, a method independent of the dose per pulse. The results of the comparison support the conclusion that one of the models is more adequate to correct for ion recombination, even in high-dose-per-pulse conditions, provided that the fraction of free electrons is properly assessed. In this respect the drift velocity and the time constant for attachment of electrons in the air of the chamber cavity are rather critical parameters because of their dependence on chamber dimensions and operational conditions. Finally, a determination of the factor k(s) was also made by zero extrapolation of the 1/Q versus 1/V saturation curves, leading to the conclusion that this method does not provide consistent results in high-dose-per-pulse beams.

Calibration↗
PubMed2004

Involvement of human p53 in induced intrachromosomal recombination in Saccharomyces cerevisiae.

p53 tumor suppressor protein plays a key role in maintaining genomic integrity and regulating growth control following exposure to DNA-damaging agents. Moreover, it is likely to control genome stability by affecting homologous recombination. p53 can work as a transcription factor in Saccharomyces cerevisiae, therefore this organism represents a good genetic model in which to investigate the molecular mechanism and genetic control of DNA damage-induced recombination. We expressed wild-type human p53 and a mutated form lacking transcriptional activity in S.cerevisiae strain RS112, which carries a synthetic intrachromosomal recombination substrate, and the frequencies of spontaneous and DNA damage-induced homologous recombination were determined. While an increase in intrachromosomal recombination induced by both UV radiation and methylmethane sulphonate (MMS) was observed in yeast cells carrying the void plasmid, p53 expression significantly reduced recombination frequency. The mutated p53 significantly reduced UV-induced recombination but had no effect on MMS-induced recombination. Our results suggest that human p53 inhibits homologous recombination induced by UV and MMS by mechanisms involving stabilization and/or phosphorylation of the protein.

Blotting, Western↗
PubMed1997

How many HIV-infected individuals may be defined as long-term nonprogressors? A report from the Italian Seroconversion Study. Italian Seroconversion Study Group (ISS)

We prospectively examined a cohort of HIV-positive persons with an accurately estimated date of HIV seroconversion who were infected through injecting drug use or sexual contact to estimate the proportion of long-term nonprogressors (LTNP), considering four definitions of LTNPs. We also evaluated whether factors such as gender, age, and HIV-exposure category were associated with being LTNP; we determined the overlap among the definitions and compared the CD4 and CD8 counts and the CD4/CD8 decline among LTNPs and "moderate" and "fast" progressors. Of the 528 persons selected for analysis, 2 to 4% were considered LTNPs, depending on the definition. The proportion of LTNPs varied by definition, and there was little overlap among definitions. The LTNPs did not appear to differ from "moderate" and "fast" progressors with regard to main demographic characteristics, and they showed a better trend of immunological parameters, appearing to have a slower progression rather than a permanently arrested infection.

Adolescent↗
PubMed1996

Herpes zoster and progression to AIDS in a cohort of individuals who seroconverted to human immunodeficiency virus. Italian HIV Seroconversion Study.

A prospective study of 1,198 individuals who seroconverted to human immunodeficiency virus (HIV) was conducted to estimate the incidence and determinants of herpes zoster and to determine whether herpes zoster can accelerate the progression to AIDS. Herpes zoster was diagnosed for 48 individuals (4%). After adjusting for the CD4 cell count, individuals acquiring HIV infection through sexual contact were more likely to have herpes zoster than were injection drug users (relative hazard, 1.50). The crude relative hazard of AIDS for individuals who had herpes zoster compared with those without herpes zoster was 2.44; the adjusted relative hazard was 1.08. After adjusting for the CD4 cell count, fever was the only specific characteristic of herpes zoster that was significantly associated with a more rapid progression to AIDS (relative hazard, 6.52). Data suggest that herpes zoster occurs more frequently in individuals acquiring HIV infection through sexual transmission. There was no evidence that herpes zoster per se is an independent cofactor of progression of HIV disease, although febrile episodes of herpes zoster may predict a faster progression to AIDS.

AIDS-Related Opportunistic Infections↗
PubMed1992

Angiographically occult brainstem vascular malformation: a longitudinal comparison of magnetic resonance imaging (MRI) and multimodal evoked potential (EP) recordings.

Over a period of several years, a patient with angiographically occult vascular malformation (AOVM) involving the brainstem was longitudinally studied by means of serial Magnetic Resonance Imaging (MRI) and multimodal Evoked Potential (EP) recordings (visual-VEP, brainstem auditory-BAEP, somatosensory--SEP--by stimulating median and peroneal nerves). MRI did contribute to an accurate definition of AOVM features. In particular, it was able to follow over time the AOVM size, and to discriminate between recent and old bleedings. Multimodal EP recordings displayed different pathological BAEP and peroneal SEP values, which documented a transient segmental brainstem involvement (related to the presence of hemorrhage), along with persistent and probably irreversible signs of diffuse brainstem dysfunction. Thus, MRI and EP assessment is useful in monitoring the clinical course of brainstem occult vascular malformations.

Brain Neoplasms↗
PubMed1991

5-aminosalicylic acid in the prevention of relapses of Crohn's disease in remission: a long-term study.

The aim of the study was to evaluate the efficacy of 5-aminosalicylic acid (5-ASA) in maintaining the remission in patients with inactive Crohn's disease over a period of three years, using either the Crohn's Disease Activity Index (CDAI) and or the Laboratory Index (LI). Thirty-eight patients entered in the study; 20 received 5-ASA 1.6 g/day and 18 no specific therapy. The patients were followed for three years. Of the patients, 86% presented a relapse, 80% in the 5-ASA group and 94% in the control group. Two patients requested surgical therapy. All patients with clinical relapse had CDAI greater than 150 and LI greater than 100. 5-Aminosalicylic acid was well tolerated and was able to protect from relapse up to 60% of the patients in the first year of therapy. When treatment with 5-ASA is prolonged for periods longer than one year a progressive increase in the number of patients who present relapse can be observed, but of the 5-ASA group, 80% of relapses occurred in the three years whereas the control group showed 94% relapses at the end of the first year.

Adult↗
PubMed1989

Dermatoglyphics in von Recklinghausen neurofibromatosis.

We studied dermatoglyphic traits in 27 patients (12 males and 15 females) with neurofibromatosis type I (NF-1) to verify which characteristics may be considered typical of this disorder. The frequency of digital central pockets in the patients was significantly greater than in control individuals (P less than .005), but when we evaluated the sexes separately, the difference was significant only among females (P less than .002). The distribution of central pockets on the various fingers was significantly different in affected females, compared with normal controls, but only on fingers II (P less than .05), IV (P .002), and V (P less than .05). The quantitative finger tip pattern values and the total finger ridge count (TFRC) were always higher in the patients, as well as was the a-b ridge count. The latter was significantly increased only on the right hand in females (P less than .01). Among the patients, the atd angle values were increased on both hands of females and on the right hand in males, whereas both the ulnar index A'-d and the a-t' ridge counts were diminished. The frequency of high endings (5' or 5") of line A was increased in NF-1 patients on both hands. Like in previous investigations, our patients showed an increased number of secondary creases, limited to II degree according to Vormittag et al. [1986] (P less than .048). Our results only partially confirmed prior data. Therefore, we think that there is no typical dermatoglyphic pattern in NF-1 and that this parameter is not a diagnostic indicator in this disorder.

Adolescent↗
PubMed1989

Enamel defects in a case of Menkes' syndrome.

A patient affected by Menkes' syndrome presents some dental abnormalities, such as enamel defects, delayed eruption and a biconically shaped incisor. The deficient action of a cuproenzyme in this syndrome leads us to hypothesize an explanation of defective enamel formation.

Brain Diseases, Metabolic↗
PubMed1987

The effects of prolonged administration of cimetidine or pirenzepine on gastric mucosal cell kinetics, serum gastrin levels and acid secretory responses in rats.

60 days' treatment of rats with cimetidine 160 mg/kg/die per os produced a significant increase in total gastrin cell number, gastrin cell density of antral mucosa as well as parietal cell density of fundic mucosa as compared with controls. By contrast, the same parameters significantly decreased in rats treated for 60 days with pirenzepine 16 mg/kg/die per os. Under the same conditions, immunoreactive serum gastrin levels were found to be significantly enhanced in cimetidine-treated rats, but not significantly changed in rats treated with pirenzepine. 48 hours after drug withdrawal, gastric secretory responses to pentagastrin were found to be significantly increased in cimetidine-treated rats and decreased in pirenzepine-treated rats. These results suggest that a feed-back reaction to cimetidine-induced prolonged hypochlorhydria mediates hyperactivity of the gastrin cell system which, in turn, induces parietal-cell hyperplasia. The hyperplasia accounts for hypersecretive responses in cimetidine-treated rats. The inhibitory activity displayed by pirenzepine on the same parameters may be due to the blockade of vagal trophic influences on gastric mucosal cells and/or to the release of inhibitory factors such as somatostatin.

Animals↗